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How would I make a collider that stops the game when it collides with the "character"?

I'm still pretty new to this, so I don't know how to create a collider. My end goal is to have a game like the chrome dinosaur game. Same principles, and all. My question is, though, how do I even make a collider. I will be using a .gif for the "dinosaur". I'd like to make it where if this collider were to touch another collider, the game stops and a "game over" is shown. I have tried to create a collider, but they just keep showing up underneath the screen where the game is shown. Ant tips, tricks, or advice? Thanks
Code is as follows:
let img; //background
var bgImg; //also the background
var x1 = 0;
var x2;
var scrollSpeed = 4; //how fast background is
let music; //for music
let catBus; //catbus
//collider variables
let tinyToto;
let tiniestToto;
let hin;
let totoWithBag;
let noFace;
let happySoot;
var mode; //determines whether the game has started
let gravity = 0.2; //jumping forces
let velocity = 0.1;
let upForce = 7;
let startY = 730; //where cat bus jumps from
let startX = 70;
let totoX = 900;
let totoY = 70;
let tinToX = 900;
let tinToY = 70;
var font1; //custom fonts
var font2;
p5.disableFriendlyErrors = true; //avoids errors
function preload() {
bgImg = loadImage("backgwound.png"); //importing background
music = loadSound("catbus theme song.mp3"); //importing music
font1 = loadFont("Big Font.TTF");
font2 = loadFont("Smaller Font.ttf");
//tinyToto.setCollider("rectangle",0,25,75,75)
}
function setup() {
createCanvas(1000, 1000); //canvas size
img = loadImage("backgwound.png"); //background in
x2 = width;
music.loop(); //loops the music
catBus = {
//coordinates for catbus
x: startX,
y: startY,
};
/*
tinyToto = {
x: totoX,
y: totoY,
}
tinTo = {
x : tinToX,
y: tinToY,
}
*/
catGif = createImg("catgif.gif"); //creates catbus
catGif.position(catBus.x, catBus.y); //creates position
catGif.size(270, 100); //creates how big
/*
tinyToto = createImg("TinyToto.gif")
tinyToto.position(tinyToto.x, tinyToto.y)
tinyToto.size(270,100)
tiniestTo = createImg("tiniest Toto.gif")
tiniestTo.position(tinToX.x, tinToY.y)
tiniestTo.size(270,100)
*/
mode = 0; //game start
textSize(50); //text size
}
function draw() {
let time = frameCount; //start background loop
image(img, 0 - time, 0);
image(bgImg, x1, 2, width, height);
image(bgImg, x2, 2, width, height);
x1 -= scrollSpeed;
x2 -= scrollSpeed;
if (x1 <= -width) {
x1 = width;
}
if (x2 <= -width) {
x2 = width;
} //end background loop
fill(128 + sin(frameCount * 0.05) * 128); //text colour
if (mode == 0) {
textSize(20);
textFont(font1);
text("press SPACE to start the game!", 240, 500); //what text to type
}
fill("white");
if (mode == 0) {
textSize(35);
textFont(font2);
text("CATBUS BIZZARE ADVENTURE", 90, 450); //what text to type
}
catBus.y = catBus.y + velocity; //code for jumping
velocity = velocity + gravity;
if (catBus.y > startY) {
velocity = 0;
catBus.y = startY;
}
catGif.position(catBus.x, catBus.y);
//setCollider("tinyToto")
}
function keyPressed() {
if (keyCode === 32 && velocity == 0) {
//spacebar code
mode = 1;
velocity += -upForce;
}
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/p5.js/1.4.0/p5.min.js"></script>

well, this is how I would generally do that kind of thingy:
function draw(){
for(let i in objects) // objects would be cactuses or birds
if(objects[i].x > player.x &&
objects[i].x < player.x + player.width &&
objects[i].y > player.y &&
objects[i].y < player.y + player.height){
noLoop()
// maybe do something else here
} // you could also use: for(let object of objects)
}
or if you want to do class stuff:
let player = new Player()
class Entity {
hasCollided_pointRect(_x, _y, _width, _height){
if(this.x > _x &&
this.x < _x + _width &&
this.y > _y &&
this.y < _y + _height){
return true
}
}
}
class Cactus extends Entity {
update(){
if(hasCollided_pointRect(player.x, player.y, player.width, player.height))
lossEvent()
}
}
class Player {
// ...
}
function lossEvent(){
noLoop()
}
this is a pretty classy way to do it and for a small game you really don't need all of this
also MDN has a nice article on rect with rect & point with rect collisions,
point with point collision is just (x == x && y == y)
https://developer.mozilla.org/en-US/docs/Games/Techniques/2D_collision_detection
this is one of my recent loss "functions":
if(flag.health <= 0){
noLoop()
newSplashText("You lost!\nPress F5 to restart!", "center", "center", 1)
}

The way I handled game states in my Processing games was by making seperate classes for them. Then my main sketch's draw function looked something like
fun draw()
{
currentState.draw();
}
Each gamestate then acted as their own sketches (for example a menu screen, playing, game over, etc), and had a reference to the main sketch which created the states. They would then alter the main's currentState to, i.e., a new GameOverState() etc. where needed.
For now, don't worry about doing that too much if all you want a really simple gameoverscreen with an image and some text.
I would suggest a structure like this instead. Use this pseudocode in your main draw function:
fun draw()
{
if (gameOver)
{
// show game over screen
img(gameOver);
text("game over!");
// skip rest of the function
return;
}
// normal game code goes here
foo();
bar();
// update game over after this frame's game code completes
gameOver = checkGameOver();
}
Now you need a way of checking for a collision to determine the result of checkGameOver()
For the collision handling, check out Jeffrey Thompson's book/website on collision handling. It's an amazing resource, I highly recommend you check it out.
From the website I just linked, here's an excerpt from the website talking about handling collisions between 2d rectangles.
And here's a modified version of the collision handling function listed there (I updated the variable names to be a little more intuitive)
boolean rectRect(float rect1X, float rect1Y, float rect1Width, float rect1Height, float rect2X, float rect2Y, float rect2Width, float r2h)
{
// are the sides of one rectangle touching the other?
if (rect1X + rect1Width >= rect2X && // r1 right edge past r2 left
rect1X <= rect2X + rect2Width && // r1 left edge past r2 right
rect1Y + rect1Height >= rect2Y && // r1 top edge past r2 bottom
rect1Y <= rect2Y + r2h)
{ // r1 bottom edge past r2 top
return true;
}
return false;
You can use that function in your checkGameOver() function which would return a bool depending on whether your collision criteria are met.
For your game, you would loop over every obstacle in your game and check whether the dino and the obstacle overlap.
Pseudocode:
boolean checkGameOver()
{
foreach (Obstacle obstacle in obstacles)
{
if (rectRect(dino, obstacle))
{
return true;
}
}
return false;
}

How to detect the side on which collision occured

This is my first post so I'm trying to make my problem as clear as possible. I'm making a game and I want to improve my collision detection. This is because I want to check what side is being hit and stop the player from moving past it without using something general like if(collision(player, enemy)) player.x = enemy.x - player.w(width) because if the player were to collide with the top it wouldn't keep the player on top.
In the code it checks if any one of the statements is true and then returns it but it doesn't tell me which statement was the one that was equal to true so I can stop the player from moving accordingly, if that makes sense. If you have a more efficient collision detection for me to use it would be greatly appreciated.
I've already tried to make a position variable to be equal to whatever side gets collided into and then stop the player from moving past it but it only works for the left side and won't let my player jump over the enemy or block.
function collision(object1, object2) {
return !(
object1.x > object2.x + object2.w ||
object1.x + object1.w < object2.x ||
object1.y > object2.y + object2.h ||
object1.y + object1.h < object2.y
)
}
//Only works for the left side
if(collision(player, enemy)) player.x = enemy.x - player.w
I expect it to be able to tell me what side is being collided into and then either stop the player from moving past/into it and for the player to be able to be on top of the block/enemy without just being pushed to the left.

You'll want to calculate the distance between the x's and y's and also use the minimum distance that they could be colliding along each axis to find the depth along both axes. Then you can pick the smaller depth and move along that one. Here's an example:
if(collision(player, enemy)){
// Most of this stuff would probably be good to keep stored inside the player
// along side their x and y position. That way it doesn't have to be recalculated
// every collision check
var playerHalfW = player.w/2
var playerHalfH = player.h/2
var enemyHalfW = enemy.w/2
var enemyHalfH = enemy.h/2
var playerCenterX = player.x + player.w/2
var playerCenterY = player.y + player.h/2
var enemyCenterX = enemy.x + enemy.w/2
var enemyCenterY = enemy.y + enemy.h/2
// Calculate the distance between centers
var diffX = playerCenterX - enemyCenterX
var diffY = playerCenterY - enemyCenterY
// Calculate the minimum distance to separate along X and Y
var minXDist = playerHalfW + enemyHalfW
var minYDist = playerHalfH + enemyHalfH
// Calculate the depth of collision for both the X and Y axis
var depthX = diffX > 0 ? minXDist - diffX : -minXDist - diffX
var depthY = diffY > 0 ? minYDist - diffY : -minYDist - diffY
// Now that you have the depth, you can pick the smaller depth and move
// along that axis.
if(depthX != 0 && depthY != 0){
if(Math.abs(depthX) < Math.abs(depthY)){
// Collision along the X axis. React accordingly
if(depthX > 0){
// Left side collision
}
else{
// Right side collision
}
}
else{
// Collision along the Y axis.
if(depthY > 0){
// Top side collision
}
else{
// Bottom side collision
}
}
}
}
Working example
Here's a working example that you can play around with. Use the arrow keys to move the player around.
player = {
x: 9,
y: 50,
w: 100,
h: 100
}
enemy = {
x: 100,
y: 100,
w: 100,
h: 100
}
output = document.getElementById("collisionType");
canvas = document.getElementById("canvas");
ctx = canvas.getContext("2d")
function collision(object1, object2) {
return !(
object1.x > object2.x + object2.w ||
object1.x + object1.w < object2.x ||
object1.y > object2.y + object2.h ||
object1.y + object1.h < object2.y
)
}
function draw() {
ctx.clearRect(0, 0, 400, 400)
ctx.lineWidth = "5"
ctx.beginPath();
ctx.strokeStyle = "red";
ctx.rect(player.x, player.y, player.w, player.h);
ctx.stroke();
ctx.beginPath();
ctx.strokeStyle = "blue";
ctx.rect(enemy.x, enemy.y, enemy.w, enemy.h);
ctx.stroke();
}
function handleCollision() {
if (collision(player, enemy)) {
var playerHalfW = player.w / 2
var playerHalfH = player.h / 2
var enemyHalfW = enemy.w / 2
var enemyHalfH = enemy.h / 2
var playerCenterX = player.x + player.w / 2
var playerCenterY = player.y + player.h / 2
var enemyCenterX = enemy.x + enemy.w / 2
var enemyCenterY = enemy.y + enemy.h / 2
// Calculate the distance between centers
var diffX = playerCenterX - enemyCenterX
var diffY = playerCenterY - enemyCenterY
// Calculate the minimum distance to separate along X and Y
var minXDist = playerHalfW + enemyHalfW
var minYDist = playerHalfH + enemyHalfH
// Calculate the depth of collision for both the X and Y axis
var depthX = diffX > 0 ? minXDist - diffX : -minXDist - diffX
var depthY = diffY > 0 ? minYDist - diffY : -minYDist - diffY
// Now that you have the depth, you can pick the smaller depth and move
// along that axis.
if (depthX != 0 && depthY != 0) {
if (Math.abs(depthX) < Math.abs(depthY)) {
// Collision along the X axis. React accordingly
if (depthX > 0) {
output.innerHTML = "left side collision"
} else {
output.innerHTML = "right side collision"
}
} else {
// Collision along the Y axis.
if (depthY > 0) {
output.innerHTML = "top side collision"
} else {
output.innerHTML = "bottom side collision"
}
}
}
} else {
output.innerHTML = "No collision"
}
}
keyStates = []
function handleKeys() {
if (keyStates[39]) {
player.x += 2 //Move right
} else if (keyStates[37]) {
player.x -= 2 //Move left
}
if (keyStates[38]) {
player.y -= 2 //Move up
}
if (keyStates[40]) {
player.y += 2 //Move down
}
}
function main() {
handleKeys();
draw();
handleCollision();
window.requestAnimationFrame(main);
}
window.onkeydown = function(e) {
keyStates[e.keyCode] = true
}
window.onkeyup = function(e) {
keyStates[e.keyCode] = false
}
main();
<h2 id="collisionType"></h2>
<canvas id="canvas" width='300' height='300'></canvas>
Reacting to the collision
Now that you know the side the collision happened on, it should be fairly trivial to decide how to react. It would be very similar to what you are currently doing for the left side just flip some signs around and change the axis.
Other Considerations
You may want to take into account your player's velocity (if it has one) otherwise the detection may fail.
If the player's velocity is too high, it might 'tunnel' through the enemy and no collision will be detected.
The player's movement can also look jittery if the velocity is not stopped upon collision
Can your objects rotate or have more than 4 sides? If so, you'll probably want to use another method as described below.
Here's a good answer to another post that talks in depth about collision engines
Other Methods
As for other collision detection methods, there's quite a few but one that comes to mind is Separating Axis Theorem which is a little more complex than what you have but will work with more complex convex shapes and rotation. It also tells you the direction and distance needed to move to resolve the collision. Here's a site that has interactive examples and goes in-depth on the subject. It doesn't appear to give a full implementation but those can be found other places.

Inconsistent AABB collision detection

I asked this question on gamedev yesterday but nobody has replied.
I'm making a 2d endless jumper as my first game and I'm running into some problems with the one-way collision detection between the player and the platform.
Collisions are detected correctly most of the time but occasionally the player inexplicably falls through the platform.
I suspect that it is ghosting through the platforms but I can't see why and I'm too close to it to be able to identify the source of the problem.
My code:
for (i = 0, len = this._platforms.length; i < len; i++) {
var p = this._platforms[i];
// Get difference between center of player and center of platform
p.proximity = Math.abs(p.x / 2 - player.x / 2) + Math.abs(p.y / 2 - player.y / 2);
if (p.closest()) {
if (p.collision()) {
player.onplatform = true;
player.y = p.y - player_s_right.height;
} else {
player.onplatform = false;
}
}
...
}
It loops through the platform objects, running the collision test only if the current platform is the closest one to the player.
Here are the closest() and collision() checks respectively:
// Return whether platform is the closest one to the player
Platform.prototype.closest = function() {
var minprox = Math.min.apply(Math, platforms._platforms.map(function (obj) {
return obj.proximity;
}));
return this.proximity === minprox;
}
// Collision detection
Platform.prototype.collision = function() {
// offset of 15 pixels to account for player's bandana
var px = player.direction > 0 ? player.x + 15 : player.x,
px2 = player.direction > 0 ? player.x + player_s_right.width : player.x + player_s_right.width - 15,
py = player.y + player_s_left.height,
py2 = player.y + player_s_right.height + player.yvelocity,
platx2 = this.x + platform_s.width,
platy2 = this.y + platform_s.height;
if (((px > this.x && px < platx2) || (px2 > this.x && px2 < platx2)) && (py2 >= this.y && py2 <= platy2) && py <= this.y) {
return true;
}
};
If anyone can shed some light on this I'd really appreciate it.

Smooth character movement on an Isometric map

I have an Isometric engine that I am building:
http://jsfiddle.net/neuroflux/09h43kz7/1/
(Arrow keys to move).
I am updating the Engine.player.x and Engine.player.y to move the character, but (obviously) the player just "pops" from one tile to another.
I wondered if there was a way to make him "slide" from tile to tile?
Or better still, free movement...
I've been pulling my hair out trying.
Here's the relevant code:
var Engine = {
// canvas variables
canvas: null,
ctx: null,
// map
map: [
[2,2,2,2,2,2,2,2,2,2,2,2,2,2,2],
[2,1,1,1,1,1,1,1,1,1,1,1,1,1,2],
[2,1,1,0,0,1,1,1,1,0,0,0,1,1,2],
[2,2,1,0,0,0,0,1,0,0,0,0,1,1,2],
[2,2,1,1,1,1,0,0,0,0,1,0,0,1,2],
[2,2,2,2,2,1,0,0,0,1,0,0,0,1,2],
[2,2,1,1,1,1,0,0,0,0,0,0,0,1,2],
[2,1,1,0,1,0,0,0,0,1,1,0,0,1,2],
[2,1,0,0,0,0,0,1,0,0,0,0,0,1,2],
[2,1,0,0,0,0,0,0,0,0,1,0,0,1,2],
[2,1,0,0,0,0,1,0,0,0,0,0,0,1,2],
[2,1,0,1,1,0,0,0,0,1,0,0,0,1,2],
[2,1,0,0,0,0,0,0,0,0,1,0,1,1,2],
[2,1,1,1,1,1,1,1,1,1,1,1,1,1,2],
[2,2,2,2,2,2,2,2,2,2,2,2,2,2,2]
],
// player info
player: {
x:1,
y:1
},
// tile size
tileH: 31,
tileW: 63,
// map position
mapX: window.innerWidth/2,
mapY: window.innerHeight/3,
// tile images
tileSources: [
"images/stone.png",
"images/grass.png",
"images/water.png",
"images/ralph.png"
],
// for pre-loading
tileGraphics: [],
tilesLoaded: 0,
// image preloader
loadImages: function() {
for (var i = 0; i < Engine.tileSources.length; i++) {
Engine.tileGraphics[i] = new Image();
Engine.tileGraphics[i].src = Engine.tileSources[i];
Engine.tileGraphics[i].onload = function() {
Engine.tilesLoaded++;
if (Engine.tilesLoaded === Engine.tileSources.length) {
Engine.draw();
}
}
}
},
// update logic
update: function() {
Engine.draw();
},
// draw the scene
draw: function() {
Engine.ctx.clearRect(0, 0, Engine.canvas.width, Engine.canvas.height);
var drawTile;
for (var i = 0; i < Engine.map.length; i++) {
for (var j = 0; j < Engine.map[i].length; j++) {
drawTile = Engine.map[i][j];
Engine.ctx.drawImage(Engine.tileGraphics[drawTile], (i - j) * Engine.tileH + Engine.mapX, (i + j) * Engine.tileH / 2 + Engine.mapY);
if (Engine.player.x === i && Engine.player.y === j) {
Engine.ctx.drawImage(Engine.tileGraphics[3], (i - j) * Engine.tileH + Engine.mapX, (i + j) * Engine.tileH / 2 + Engine.mapY - Engine.tileH + 10);
}
}
}
Engine.gameLoop();
},
// game loop
gameLoop: function() {
Engine.gameTimer = setTimeout(function() {
requestAnimFrame(Engine.update, Engine.canvas);
}, 1);
},
// start
init: function() {
Engine.canvas = document.getElementById("main");
Engine.canvas.width = window.innerWidth;
Engine.canvas.height = window.innerHeight;
Engine.ctx = Engine.canvas.getContext("2d");
document.addEventListener("keyup", function(e) {
//console.log(e.keyCode);
switch(e.keyCode) {
case 38:
if (Engine.map[Engine.player.x-1][Engine.player.y] !== 2) {
Engine.player.x--;
}
break;
case 40:
if (Engine.map[Engine.player.x+1][Engine.player.y] !== 2) {
Engine.player.x++;
}
break;
case 39:
if (Engine.map[Engine.player.x][Engine.player.y-1] !== 2) {
Engine.player.y--;
}
break;
case 37:
if (Engine.map[Engine.player.x][Engine.player.y+1] !== 2) {
Engine.player.y++;
}
break;
}
});
Engine.loadImages();
}
}
// loaded
window.onload = function() {
Engine.init();
};
// request animation frame
window.requestAnimFrame = (function(){
return window.requestAnimationFrame ||
window.webkitRequestAnimationFrame ||
window.mozRequestAnimationFrame ||
window.oRequestAnimationFrame ||
window.msRequestAnimationFrame ||
function (callback, element){
fpsLoop = window.setTimeout(callback, 1000 / 60);
};
}());
Thanks in advance!

You are drawing the character at tile positions. What you want is to just add a second set of coordinates for the character representing its destination. To move smoothly you can set the characters position in fractions of a tile. Eg player.x = 2.5 the character is halfway between tiles 2 and 3.
Also you want to get rid of the messing about in isometric space. Off load the transformation from 2d to isometric to the draw function, rather than doing it by hand each time you draw to the playfield.
Create the draw function
// add to the Engine object.
// img is the image to draw. x and y are the tile locations.
// offsetX and offsetY [optional] are pixel offsets for fine tuning;
drawImageIso:function (img,x,y,offsetX,offsetY){
offsetX = offsetX === undefined ? 0: offsetX; // so you dont have to
offsetY = offsetY === undefined ? 0: offsetY; // add the offset if you
// are not using it;
Engine.ctx.drawImage( // draw the image
img,
(x - y) * Engine.tileH + Engine.mapX + offsetX,
(x + y) * Engine.tileH / 2 + Engine.mapY - Engine.tileH+offsetY
);
},
Change the player object to
player: {
x:1,
y:1,
destX:1, // the destination tile
destY:1,
playerAtDest:true, // true if the player has arrived
},
Add this befor the tile render loops
var p = Engine.player; // because I am lazy and dont like typing.
var dx = p.destX;
var dy = p.destY;
var maxPlayerSpeed = 0.1; // max speed in tiles per frame
var mps = maxPlayerSpeed; // because I am lazy
// check if the player needs to move
if( Math.abs(p.x - dx) > mps || Math.abs(p.y - dy) > mps ){
p.x += Math.max( -mps , Math.min( mps , dx - p.x )); // move to destination clamping speed;
p.y += Math.max( -mps , Math.min( mps , dy - p.y ));
p.playerAtDest = false; // flag the player is on the way
}else{
// player directly over a till and not moving;
p.x = dx; // ensure the player positioned correctly;
p.y = dy;
p.playerAtDest = true; // flag the player has arrived
}
Add the following where you used to draw the player. Use the destination x,y to determine when to draw or use Math.round(Engine.player.x) and y to determine when.
// now draw the player at its current position
Engine.drawImageIso( Engine.tileGraphics[3] , p.x , p.y , 0 , 10);
You will have to change the interface to move player destination rather than x and y. You may also want to delay the move until the player has arrived at the current destination.
That covers the basics.

how to stop an object when it collides with another object in javascript canvas

OK, so I am making a Pacman game using HTML5 . the problem is whenever I hit one of the brick blocks I want the sprite to stop moving but it keeps going until it hits the left most brick object.
how do I fix this? please help... here is the code I'm using to make the sprite stop.
here is all my code, if you have time, please parse it, and tell me what I have done wrong.
function init(){
var canvas=document.getElementById("ctx");
var ctx = canvas.getContext("2d");
var player = {sx:6,sy:6,sw:15,sh:15,x:230,y:377,w:20,h:20}
var ss = new Image();
ss.src="SS.png";
var right=false,left= true,up = false,down = false
var b = [{x:0,y:0,w:25,h:((canvas.height/2)-25)},{x:0,y:((canvas.height/2)),w:25,h:((canvas.height/2))},{x:50,y:25,w:50,h:50},{x:125,y:25,w:75,h:50},{x:225,y:0,w:25,h:75},{x:275,y:25,w:75,h:50},{x:375,y:25,w:50,h:50},{x:50,y:100,w:50,h:25},{x:125,y:100,w:25,h:125},{x:125,y:150,w:75,h:25},{x:175,y:100,w:125,h:25},{x:225,y:125,w:25,h:50},{x:325,y:100,w:25,h:125},{x:275,y:150,w:75,h:25},{x:375,y:100,w:50,h:25},{x:25,y:150,w:75,h:75},{x:375,y:150,w:75,h:75},{x:375,y:250,w:75,h:75},{x:25,y:250,w:75,h:75},{x:125,y:250,w:25,h:75},{x:325,y:250,w:25,h:75},{x:175,y:300,w:125,h:25},{x:225,y:325,w:25,h:50},{x:50,y:350,w:50,h:25},{x:75,y:350,w:25,h:75},{x:125,y:350,w:75,h:25},{x:275,y:350,w:75,h:25},{x:375,y:350,w:50,h:25},{x:375,y:350,w:25,h:75},{x:25,y:400,w:25,h:25},{x:125,y:400,w:25,h:75},{x:50,y:450,w:150,h:25},{x:275,y:450,w:150,h:25},{x:325,y:400,w:25,h:50},{x:425,y:400,w:25,h:25},{x:175,y:400,w:125,h:25},{x:225,y:425,w:25,h:50},{x:450,y:0,w:50,h:((canvas.height/2)-25)},{x:450,y:(canvas.height/2),w:50,h:((canvas.height/2))}];
function gen(){
for(var i=0;i<b.length;i++){
ctx.fillStyle="blue"
ctx.fillRect(b[i].x,b[i].y,b[i].w,b[i].h)
}
ctx.drawImage(ss,player.sx,player.sy,player.sw,player.sh,player.x,player.y,player.w,player.h)
}
function move(){
for(var i=0;i<b.length;i++){
//((a.x + a.width) < b.x)
if(left &&
player.x > b[i].x && (player.x + player.w) < (b[i].x + b[i].w) &&
player.y > b[i].y && (player.y + player.h) < (b[i].y + b[i].h)) {
// here you can tell that the user is colliding an object
player.x-=1
}
else {
}
}
}
function animate(){
ctx.save()
ctx.clearRect(0,0,canvas.width,canvas.width);
gen()
move()
ctx.restore();
}
var ani = setInterval(animate, 30)
}
window.addEventListener("load",function(){
init()
})

First, I can see a problem with the first part of your if condition:
left = true && ...
Should be
left === true && ...
Or even better
left && ...
Now for the collision part it usually is top-left or in the middle of the object
I'd suggest this top-left origin collision check:
if(left &&
(player.x >= b[i].x && player.x + player.w <= b[i].x + b[i].w) &&
(player.y >= b[i].y && player.y + player.h <= b[i].y + b[i].h) {
// here you can tell that the user is colliding an object
}
It checks several cases, this part
(player.x >= b[i].x && player.x + player.w <= b[i].x + b[i].w)
Will meet requirements if the player's x (with its width component) inside the occupied x range of the current object
The second part
(player.y >= b[i].y && player.y + player.h <= b[i].y + b[i].h)
Will meet requirements if the player's y (with its height component) is inside the occupied y range of the current object.
It will only execute the if statement if the condition is satisfied for both of the above cases.
You can tell if you should reposition the player on the left or on the right, by substracting the players x component to the object's x component, same goes for top or bottom with y component. The previous sentence is only valid if you move in a grid cell by cell.