javascript - Object variable is undefined -


i new oop concepts please me out here, whenever using object variable value stored in undefined. please check below code

function bubble(q, w, e) {   var x= q;   var y= w;   var r = e;   var canvas= document.getelementbyid('mycanvas');   var ctx = canvas.getcontext('2d');    ctx.beginpath();   ctx.arc(x,y,r,0,2*math.pi);   ctx.stroke(); }  var b1 = new bubble(100,100,50); var b2 = new bubble(160,160,30); alert(b1.x);

use this instead of var. var create scoped variable accessible in function scope, this attach variable current context. refer x, y, r prefix this..

function bubble(q,w,e)  {     this.x = q;     this.y = w;     this.r = e;     var canvas = document.getelementbyid('mycanvas');     var ctx = canvas.getcontext('2d');           ctx.beginpath();     ctx.arc(this.x, this.y, this.r, 0, 2*math.pi);     ctx.stroke();   }    var b1 = new bubble(100,100,50);  var b2 = new bubble(160,160,30);  alert(b1.x);
<canvas id="mycanvas"></canvas>


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