Reducing JavaScript Markup when drawing objects in HTML5

Question

I'm trying to draw a few circles that will all have the same properties, but a different endingAngle, I don't want to write the entire circle code 5 times, is there a way to either assign most of the code to a class, and just change one variable for 5 different ID's?

Here are two of the circles

var canvas = document.getElementById('firefox');
var context = canvas.getContext('2d');
context.beginPath();
context.arc(64, 64, 60, 1.5*Math.PI, .3*Math.PI, true);
context.lineWidth = 8;
context.lineCap = "round";
context.strokeStyle = '#c5731e';
context.stroke();

var canvas = document.getElementById('chrome');
var context = canvas.getContext('2d');
context.beginPath();
context.arc(64, 64, 60, 1.5*Math.PI, .9*Math.PI, true);
context.lineWidth = 8;
context.lineCap = "round";
context.strokeStyle = '#c5731e';
context.stroke();

.3*Math.PI and .9*Math.PI are the only things that are going to change between circles, any way I can write the above so I don't have to write all of it 5 times?

Answer 1

You don't have to change your markup, you can do this :

['firefox','chrome'].forEach(function(id, index){
    var canvas = document.getElementById(id);
    var context = canvas.getContext('2d');
    context.beginPath();
    context.arc(64, 64, 60, 1.5*Math.PI, (index+1)*0.3*Math.PI, true);
    context.lineWidth = 8;
    context.lineCap = "round";
    context.strokeStyle = '#c5731e';
    context.stroke();
});

You don't have to duplicate the code or to call a function, you just have to add elements in the array.

If you can't infer the angle from the index, then,

• either you want to "hardcode" the data, then use a function (see other answer)
• or you want to manage the data as data.

In the latter case, you can do something like this :

 var data = [
   {id:'firefox', angle:33},
   {id:'chrome', angle:43}
 ];
 data.forEach(function(e){
    var canvas = document.getElementById(e.id);
    var context = canvas.getContext('2d');
    context.beginPath();
    context.arc(64, 64, 60, 1.5*Math.PI, e.angle, true);
    context.lineWidth = 8;
    context.lineCap = "round";
    context.strokeStyle = '#c5731e';
    context.stroke();
});