How to make multiple elements in a canvas
Question
I'm trying to show multiple pipes in the canvas of same height but even after using a for loop it is showing a single pipe and not a lot of it
<script>
var tryCanvas = document.getElementById("myCanvas");
var c = tryCanvas.getContext("2d");
var myCall = [];
function Squares() {
for(var i =0; i < 10; i++){
this.x = Math.random()* tryCanvas.clientWidth;
this.y = 0;
this.w = 20;
this.h = 60;
this.counter = 0;
this.draw = function() {
c.beginPath();
c.rect(this.x, this.y, this.w, this.h)
c.fill();
}
}
this.update = function() {
if(this.x < 0){
this.x = 0;
}
this.x -= 1;
this.draw();
}
}
var holder = new Squares;
setInterval(callFun, 10);
function callFun() {
c.clearRect(0,0,tryCanvas.clientWidth, tryCanvas.clientHeight);
holder.update();
}
</script>
If I push the constructor function in an array it's not showing anything in the canvas and in the console it's giving undefined or NaN. But if I do it without "this" its generating the number of rects. What am I doing wrong here?
1 answers
solution1
2 ACCPTED 2017-08-17 06:26:53
Updated to move the bars along the screen
See this working example: https://codepen.io/bkfarns/pen/braWQB?editors=1010
This.draw will only get created with the values from the last iteration of the for loop.
Also as a side node, usually instead of new Squares you call the constructor like new Squares() . When you call the constructor you are calling a method.
But I think the code below fixes your issues. Try it out:
<body>
<canvas id="myCanvas"/>
</body>
<script>
var tryCanvas = document.getElementById("myCanvas");
var c = tryCanvas.getContext("2d");
var myCall = [];
function Squares() {
this.draw = function(xOffset) {
for(var i =0; i < 10; i++){
this.x = (i * xOffset) + (5*i)//Math.random()* tryCanvas.clientWidth;
this.y = 0;
this.w = 20;
this.h = 60;
c.beginPath();
c.rect(this.x, this.y, this.w, this.h)
c.fill();
}
}
}
var holder = new Squares();
var xOffset = 20;
setInterval(function() {
c.clearRect(0,0,tryCanvas.clientWidth, tryCanvas.clientHeight);
holder.draw(xOffset)
xOffset--;
}, 1000)
</script>
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