<hmtl>
<head>
<!--<script src='main.js'></script>-->
</head>
<body>
<canvas id='myCanvas'> </canvas>
<script>
function shape(x,y){
this.x=x;
this.y=y;
var canvas = document.getElementById("myCanvas");
var ctx = canvas.getContext("2d");
ctx.fillStyle = "#FF0000";
ctx.fillRect( this.x, this.y, 50, 50);
}
}
var sqr=new shape(100,100)
sqr.x+=100
</script>
</body>
</hmtl>
Despite adding 100 to x and expecting its position to be (200,100), when opening a live server it remains at the original position of (100,100).