--- title: Connect 4 game with React and Next.js slug: connect-4-game-with-react-and-next-js published_at: 2021-09-13 17:30:01 +0000 updated_at: 2026-03-04 20:13:56 +0000 summary: description: Connect four game with React and Next.js tags: [cjav_dev, web development tutorials, web development for beginners, vim, ruby, rails, javascript, building connect four with React, Connect four game with React, React.js tutorial, Connect 4 with React, Connect 4 in JavaScript, Next.js Connect 4] views: 2706 author: CJ Avilla url: https://www.cjav.dev/videos/connect-4-game-with-react-and-next-js youtube_url: https://www.youtube.com/watch?v=CjQv3VNt0HU youtube_id: CjQv3VNt0HU embed_url: https://www.youtube.com/embed/CjQv3VNt0HU thumbnail_url: https://i.ytimg.com/vi/CjQv3VNt0HU/hqdefault.jpg type: video --- # Connect 4 game with React and Next.js *Published: September 13, 2021* *Views: 2706* ## Watch [Watch on YouTube](https://www.youtube.com/watch?v=CjQv3VNt0HU) [![Connect 4 game with React and Next.js](https://i.ytimg.com/vi/CjQv3VNt0HU/hqdefault.jpg)](https://www.youtube.com/watch?v=CjQv3VNt0HU) ## Description Connect four game with React and Next.js ## Transcript hey what's up welcome back in this episode we're going to try to build out a connect 4 game using react we're going to use next js and uh yeah it should be it should be pretty fun i haven't done this before so we're just going to kind of go through the entire process from scratch of uh playing around with next this is kind of like one of the first next js apps i'm going to play with all right so we're going to use npx create next app this is a lot like create react app it's going to build out sort of a template for us and what we want to do is give it a name so we're going to call it maybe next js connect for uh connect4 and then we want to tell it to use npm for installing these dependencies and that will build out a template for us that's going to have support for react on the front end and next gs is really a whole web framework that gives us the back end and the front end we're really just going to play around on the front end today and we could have just as easily used create react app but i did want to play around with next and just to have access to all the stuff that next gives us for there's a lot of really awesome things that it has for image processing and pre-fetching pages and things like that so i think what we're going to do today is try to build out a board that will have columns so if you're not familiar why don't we pull up yeah connect four let's just take a look at some images of how this works so this is a game where you sort of put in pieces you and you put you put in pieces you drop them in from the top and then they fall down to the bottom and sort of stack up on top of each other and as they stack up uh you try to align four of them in of the same color in a row and so it's a two-player game where um yeah you just add pieces into this into this sort of uh board so i think we're gonna build out a ui and try to play this i play this all the time with my kids it's super fun so let's get at it so we're going to cd into our next connect 4 app and we're going to just npm run dev this will start up next js file successfully all right so now we see the page that uh that you get when you first start off with next.js this is sort of the welcome page um and what we're going to do is the very first thing i want to do is rip out all the stuff that's on this page so inside of an xjs app you get node modules pages public and styles we'll start off in styles and just delete all of the styles i think uh except yeah we'll just delete all the styles and then in global css we'll keep that i think it's just a reset public is where our static assets are going to go so if we have any images or whatever we'll drop those in public and then finally pages is where most of the app was the app is implemented so in index.js this is the page that comes as part of the template in this head tag that's how you can manage stuff that's sort of like in the header so this title tag will be replacing this title that's up here so we can just call that connect four and we should get hot reloading i think oh we gotta we got an error here so we can remove that now we're compiling okay and styles is not defined so yeah we're just gonna remove all of these things that say styles dot whatever um we can we can keep the main class and we'll keep the header but that's all that we really want to keep and we'll just say like play or maybe just connect 4 or something okay and then we're going to remove the rest of the template that's here because we want to implement our own the very first thing we want to do is sort of just build out a new component that renders a game some sort of connect 4 game so we're going to have a new component here called i don't know connect for game and that won't take any props in i don't think to start and it'll just return a fragment that has to start off we'll just say like let's play that should totally work all right well whatever so the connect4 game is gonna be these columns where we wanna enter tokens sort of in from the top and so what i think makes most sense is just to start off by building out our grid and i think the grid is supposed to be it looks like it's seven wide by six tall so we're gonna need to build a grid that's seven by six so i was thinking we could just iterate over like some columns or something so maybe we have some the like game state uh here in i think we could store it technically in like several arrays right where we have an array of arrays where each of these is the the um sort of the content of the column um so i don't know let's let's start with something like that and see how it goes so we're gonna say let's actually use state can i do that inside of next.js import use state from react uh game or let's see game state is going to be set state or set game state and we'll start off with a new array of seven columns and see if we can just iterate over the game state so then we want to say like uh gamestate dot map and then we want to have the column mapped to something uh let's see return column i don't know if that's going to do anything here json stringify column um let's see how about we just return x for each of those columns is this doing this is this new array thing doing what i think let's see so in the console here if we say new array of seven yeah that should give us back okay it's seven long and then we want to actually populate it with stuff can we do that no okay so it wants like um yeah okay so it wants to create we need to create all of them so let's do yeah let's do this we'll do um uh four bar i equals or maybe this is going to be the column equals zero well column is less than 10 column plus plus and or let initial initial.push new array of 6 and we'll set this as the initial value let column equal zero while column is less than seven column plus plus why is this failing here column is already declared where is it okay let column column let's see how's that c has already been declared missing semicolon all right looks like we got x's we got x's showing up that's good i'm gonna move this down below all right so we have our [Music] initial state for the columns here and then what we want to do is for each column we want to render some sort of html structure for the column data so i think we actually want to return here like a game column or something that has the column data or the column value maybe and then we need to create that so const game column is a new react component that's going to return and this is going to take in column [Music] as a prop and we want to return or return just x for now okay cool so we're still getting back x that's great and then what if we want to return a div and we'll set the class the class name for this to column and i expect the column to be populated with six items so again we want to sort of map over those so column.map cell into something where maybe we return cell i don't know let's see if we can get cells showing up here so column.map cells and right now they're empty because again we're pushing six empty things or an array with six okay so let's for now let's just do like one or yeah one two three four five six and see if we can get anything showing up here let's inspect this so right now we are getting a a bunch of columns are being rendered but they're all empty and so what i want to do is console.log column to see if we're getting anything back as we're re-rendering this okay so they are still coming in as empty why is that it should be populating them with array with six items in it right um oh okay i just need for some reason he did a hard refresh it's so odd and it's like unclear when this is actually going to automatically reload each child in a list should have a unique key prop okay sure now we've got the cells showing up but we probably want to render these as maybe like a span or something where the content of the span is going to be the actual value that's in there so yeah i guess we do want to put in cell so whatever the content of the cell is so now we have one two three four five six one two so the columns are being rendered sideways now right and so in order to render them up and down we need to write a little bit of javascript i think right and so maybe we can do that here so there's a really cool thing in next.js you can use styled css you can say style jsx and then um with an open tick and then you can write your your css here so if we have um a game column okay so we've got our column let's give this a class name of cell maybe and we'll call this like dot column and each column should be display flex and each cell should be flex row one and the width or i guess the um then we also need sort of like a general class that wraps the entire board so maybe we'll do that here div class name is board okay and the board is also going to be display flex and okay so now we've got something going on here all right so let's make the cell have a border just so we can see what we're looking at and what we're working with also i'm not sure if you can see this i'll make it a little bigger here so the cell we're going to give it a a border of 1 pixel wide solid red just so we can see what's around the cell and we'll give the column a border of 1 pixel solid blue and let's give this a little bit of padding too so we can see the difference between the columns and the in the um the cells all right we keep getting this issue with each thing needs to have a key so can we do key equals i don't know maybe we need to pass in the id here or something so when you're mapping over you can you can also get like the index of the item i believe so let's see refresh okay what's going on check the render method of game column so i thought this map method would let us get x console.log x as like oh you know what it's not like this it's like this it's not destructured it's just it's just there okay so that works i think um and then similarly with this one i think we need a key and that's gonna be um i don't know index or something we'll pass that in as like a prop when we're rendering this id uh x i don't know we'll see let's see what this looks like column comma x all right so now everything should have keys and such um what okay we're still getting an error that says we need a key prop unique key prop so we've got a key and we've got a key where else do we need keys or maybe this is not unique what is okay so let's see what's going on here inspect and huh okay why don't we see that in okay so this maybe this needs to be like um column dash index i don't know uh does that make it happy nope okay each child in a list should have i know i know i know where where are you talking about that maybe this is the one okay cell dash or does this need to have the column and the cell oh gosh um idx dash whatever uh maybe no what the okay um whatever we're just gonna keep going because that's i think it's fine um okay so we've got our board it's display flex inside of our board we have a column that's display flex and we also want this one to be like flex grow one i think and i think we want to just like flex direction column um and let's take a look in here and see what's going on so for the board for the css for the board what is that the css for the board we've got display flex flex one um that is our container all right and then inside of the column the column should also be display flex i don't know why that's not showing flex 1. let's see so on the column if we do display flex huh okay so why isn't that being applied over here do we not have class name column i wonder if this if this styled thing is only applying on the board what is it is it applying to the cell it's not okay so that's i think that might be the issue here so we want to apply the styled stuff um in the component where it's happening oh wow look at that okay so that's cool so it's now showing us um in columns it's showing us all the columns that we need that's awesome all right so the next step here is and also this is super cool it's like scoped the css is scoped to the component i really like that um because it doesn't bleed out into your other components so that's cool all right but we have a problem because i think the first item in the cell or like the first item in the um in the column this one should actually be at the bottom and so there's a cool thing with flex direction where you can do column reverse um so now this is yeah okay so now one is at the bottom two three four five six so what i want to do now i think is like make it so that you can click on a column and it will start adding things to these this data for the column um but again now we need to make this uh new array of six let's see if that works um maybe okay so that is not gonna work so we do need it to be something um that represents null that is not actually null uh let's see if this is gonna work that's not enough okay maybe oh wow okay so they're they're not tall enough now all right so now we gotta go to the cell and say like height is uh 20 pixels okay so at least we've got columns now um that are empty now what we want to do is say like when you click on one of these game columns we populate the column with something i don't know so we'll have to figure out what that is but um the thing is that the game state is being managed here in the connect four game which is the parent component to this game column so i think we actually want to pass in like something else inside of the game column maybe um the some like click event so on click uh we can pass it this something that will fire so maybe we say like add um add item or add peace i don't know add token add something okay so when we click on the column we're going to call a function in this component const add piece and that's going to do something so maybe we're going to be yeah uh i guess we could also pass in x here we would know which column it is so add piece of x and then we can see add piece for which column and then we can say game state at column i wonder if that will work as expected so console.log gamestate at column and let's also log column and hopefully that is going to do some cool stuff that we expect um maybe not so we're passing down this prop right on click prop to the game column but that hasn't actually been registered on the html components inside there because that's actually being passed down as a prop so now we have to say like on click um and then i'm just going to attach it to the column up here and just say on click do on click and i think that might do stuff i don't know let's see so nope uh oh cool great okay so that is giving us the right columns so that's cool um oh gosh okay so how do we want to do this i think what we need to do is uh when we click we need to figure out how to add the piece so maybe we also need like a current um like a cur current player or something use current player set current player and we'll we'll we'll just use x's and o's for now and so we'll have a current player when we add the piece we want to say like um we want to call set game state and update the whole game state but we want to update it such that we have added that piece into the game at that column so we actually want to we want to create a new game state that is basically the existing game state except for that one column so how do we do that um i guess we actually can get this is kind of more like the column index and so i think we want to say something like the like um the column is equal to game state at at uh column index and then what we want to do is say like um let's just put let's just put the current piece in the in the first column or like in the first cell for this for now uh current player and then we will say game or like i guess okay so we need to spread oh this is going to be tricky because we need to spread everything up to that index or we need to like create a new array of arrays ew interesting interesting interesting interesting is this how we want to do it so i'm thinking instead of using an array as like the game state here we might want to use an object so that we have specific keys and we can say something like um uh okay so gamestate.map so this is no longer a thing so now we want to get like um gamestate dot uh oh okay so we want to we want to iterate over all of the columns yeah how do we do this okay so we want to make sure that the order is maintained but i think that might be okay i think it's dot entries or something like this right so we want to get if we have like a is some object a dot entries or maybe it's object dot entries and we give it a and that gives us all the entries so if we say a is something that has like one pointing to some array and two pointing to some array and then we say entries for a that gives us back the two arrays so we can i think we can say something like object.entries for gamestate dot map and then we'll iterate over those things oh look at that okay so we we have stuff this looks really weird because um let's see so now if we click on it uh what's happening nothing all right uh console.log column index and okay odd so what oh okay so we haven't finished we haven't finished placing the pieces um so we've got our column here column at index zero is giving us back the column and we're setting it equal to the current player and the other thing that's going on or that's weird is that this entries we're like mapping over it but i don't know forgetting what we expect so um okay so this is the two arrays right and if we iterate over that dot math x and i do we get x and i as expected we do but they're in the opposite order wait why is this why does this have a 1 in it object.entries oh you know what i think this is going to give us um the key and the value right and then we need like key value yes okay okay so when we when we map over object.entries this actually gives us key and value which okay so now we're back to normal or oh the game state is being updated but it's not being updated so now we need to say set game state and we have to set this back up so that it equals um it's like we want to spread game state and we want to set a column index equal to column something like that i think no set game state to uh an object okay is that oh man oh man it's working okay so now what we need to do is figure out okay if we've already put a piece at the bottom then the current piece needs to be put on top of that piece so i gosh i really i'm really frustrated that this doesn't let me just put in nulls like uh let's see and if i refresh this oh it does okay i think they're supposed to be it's supposed to be six tall six tall so now if i put a piece in there okay so now what we want to do is figure out the first null position right and replace that with instead of just using 0 here and setting the first or like the the lowest value as x every time we click on it it should add a new piece above x how do we want to do this there's probably some fancy cool way to do this index of null or something like that like const piece position is equal to column.index of null maybe and then piece pause does that give us what we want let's see oh look at that oh my gosh holy moly okay so this is probably not like honestly like not the best way to do this but noel is telling us where there's empty spaces and then the pieces are telling us where there's the pieces so i think that's all right the next thing we want to do is like every time you place a piece you should switch the player to the other player so we want to do something like toggle toggle the player after we've done this bit so we want to set current player equal to current player if the current player is x then we wanted to set it to o otherwise set it to x something like that there might be a fancier way to do that also but oh look at that okay so um this is totally playable boom okay so that should be a win right there because this is four in a row if we take off the border and we just have like clicking on these then i think we're getting pretty close but let's put the border back and let's try to get the content in like the center of the cell so i think we can use like justify content um center maybe let's see maybe justify is it justify items center i can never remember this stuff okay just maybe that needs to go up here uh okay justify content center maybe it's a line a line items center oh gosh do i need to do display flex on this too okay so that got it up and down and then justify content center oh boom look at that okay so now we have our items and they're appearing in the center of the cells that's pretty sweet um the next thing i want to do is replace x's and o's with like some sort of emoji so let's have some fun with emojis here um what should we use i think the pieces in the game are like yellow circle and a red circle um maybe we should make these constants i don't know uh x piece is this yellow circle and then o piece is the red circle the the the benefit of having these sort of stored as constants somewhere is that we can just use them in a bunch of different places and we don't have to keep typing emojis in our code x piece and then down here we can do xps okay so now if we do all right look at that that looks sweet okay so one thing that's is missing is the satisfying feeling that happens when you slide that bottom like when you slide the bottom of connect four and all the pieces like slide down and crash out to the bottom but i think that's all right i think it's okay uh the other thing is that as you enter pieces in the width is changing which i think is all right but uh it's just kind of like weird that it grows like that um so let me know down in the comments if you are a css master how is there a better way to do this like or was this kind of the way that you would have done it um and yeah then okay so i think we've got we've got like the the rough user experience or the rough sort of ui figured out here um so i am gonna take away the red border because i think that's the most distracting and then i think that's pretty darn close to what we want the next step i guess would be to try and figure out if someone has actually won so after every time we add a piece or make a move we want to check and see if the game is over so after we have done set game state and set current player etc etc etc let's check and see if the actually we might want to do it like right here like game over um right before we swap players so let's let's make a new method game um uh if game over like alert game over i don't know we can come back and mess around with this so now we just make a new method const game over and this is going to look at the game state and try to determine if there's any four uh any four elements in a row that are the same color that are not null and that could be up and down or it could be left and right or it could be diagonal and so let's try to figure out how we might want to check and see if the game is over let's start with up and down because all of the pieces in the same column are going to that's going to be the easiest thing to check all right i'm just gonna play around here and let's let's explore let's explore so i'm gonna say how do we work from the back all right so the other the other thing that's on my mind is that if we had if we were just tracking two at a time so if we make the problem a little bit smaller and we were looking for two in a row then we might just use like a a front and a back and then just kind of work our way through and check to see like um so yeah let's let's try that so like 4 var c is equal to 0 c is less than 7 c plus plus so that's going to give us our columns okay and then we're gonna we're gonna find each column so we're gonna say let column equal game state at c so that gives us the column then we're going to say 4 var r which is the row is 0 r less than 6 r plus plus now we want to get each individual cell and we want to see is if actually i think this can actually go to six minus four um and then we wanna say like if the column at r is the same as the column at r plus one and the column at r plus one is the same as column at r plus two and the column at r plus two is the same as the column at r plus three then we have a winner i think right so return true so if game over we're gonna alert true okay so let's just see if this crazy idea here works so game over of course okay so we also want to check if it's not null so if um column at r does not equal null and okay so now we refresh oh boom game over uh but it's alerting whatever it's alerting before we see the game state but that's fine okay so that is totally working for uh check checking check if there are any four in a row in a column now let's let's let's do this let's do this again but let's set it up so that we get them in a row but on top of one another okay so that didn't work right so r is zero r zero it's not there so r is less than okay so r plus plus then r is going to be one that's still less than two and then r is one one is not null and does the cell at one equal no it doesn't okay r plus plus so that okay maybe this needs to be minus three okay so that worked all right um okay so we had an off by one error here where we were ending too early up here also instead of using column directly we could have used game state so in fact like if we just replace all this with game state or we want to replace column with game state at c um and i think that should still work let's see probably should have some automated tests or something okay cool that still works so the reason i wanted to do it that way is that that makes it easier to like sort of just swap out um yeah now let's let's make two loops okay let's keep them the same though um so now this is going to be seven minus three and this is just going to be six and then instead of r instead of r plus one now we wanna do c plus one c plus two something like that okay let's think about this for a second so if the game state at that column and row is not null and it equals the same game state at the same row that is the same as the next column over the next column over is the same as the next column over and then column over his neck okay so i think that's going to work maybe let's see boom nice okay so that is now working for these um the rows now what we need to do is check and see if there's any four in a row in a um in a diagonal i don't want to bore you with me trying to butt my head against this thing and figure out exactly the logic for how we're going to implement game over so i'm just going to bang that out and then i'm going to tell you about it in just a sec all right so now we have a game over function the way that we chose to implement this was to check and see if there were four in a row for each different sort of possible solution so this is obviously not the best right so we are looping over all of the columns and then we are checking the game state for each of those columns to see if there's any four in a row in a column again we're looping over uh similar stuff to check and see if there's any four in a row in a row and then we are looping over to check and see if there's any four in the in a diagonal up into the right and then we're checking to see if there's any four in a row that are diagonal down to the down to the right so up to the right and down to the right um so the crux of the problem here is that like as you're iterating you want to like make sure that you're not uh going out of the index or out of uh out of range right and so like as you're incrementing the adjacent cells so here we're saying like if the game stay at this specific column so this grabs a column and tells us whether or not something at that row or the row above it right or the row above that or the row above that if they're all the same then we are going to return true and so otherwise by default we'll just return false from this function return false and the game will continue on and then what we want to do down here is instead of alerting game over we'll change some game state and so we'll say you know like the winning winning player or like winner the winner and we'll say set winner and this is going to start off as null and we'll say down here when we check if the game is over we'll set set winner to current player we'll do that right before we swap the current player and i think that should store who the current player is and then down here inside of the board class we can say like if uh winner then we'll render something uh else we want to render everything else here i think is how we might want to do this um i don't know well i guess you have to do this you have to do this like winner and and thing right um so uh shoot okay so maybe we say like if winner we want to return like uh h1 and winner is the winner h1 and then otherwise we'll return all the rest of this business here that way we get a more sort of reactive feeling thing so let's see if we can oh boom yellow is the winner awesome okay refresh the page and um let's see if we can get oh red to be the winner boom red is the winner amazing all right cool so i'm gonna call one of my kids in here to play and i think it should be pretty fun all right logie okay all right let's play connect four okay so you want to go first yep okay pick a column and click on it i'll go right here oh okay nice so you're yellow i'm gonna go here okay you go wait this is can oh i think it has two did you like an electric connector yeah does it have too many yeah it's too many slots i don't think so i don't think so i think it should work okay oh i went too all right your turn okay blocked um yeah because if you play it this way yeah that's not fair okay now there's no way to make stuff unless you go up yes too many columns i'm pretty sure oh you think so okay let's see hmm let's see i'm trying to catch game oh really yeah i want to make a hat okay let's see box yeah you blocked me yeah okay go ahead in your turn nice oh [ __ ] me it's gonna be cat's game no matter what you think so oh okay your turn okay here let me go there oh oh oh i went i went too oh oh you're the winner you won oh my gosh wait did i win or did you win you won i won okay all right um go look at a connect four board on i have it i have it up okay it's right here it's the right size this is the right size i just i need you know what i need to make it more obvious yeah you need to make it smaller okay yeah right all right uh all right that was fun so we got some user feedback the user feedback is we need to make uh make the the actual slots more obvious um but yeah we can do that with css and uh yeah it was fun hopefully you enjoyed that's uh yes we played around with mostly it was just react stuff and we used style jsx inside of our inside of our game component here but um yeah and most of the time we spent actually figuring out what if the game's over or not but that was tons of fun thanks for hanging out and yeah we'll see you next time cheers [Music] --- [Back to all videos](https://www.cjav.dev/videos) --- ## Hey Agent, thanks for visiting! 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