为什么不进行画布绘制？

Question

I've looked over this code every way I can, and I'm not seeing what's tripping me up. This is my first night looking into canvas, and my first night messing with JS outside of Codecademy, so I'm sure it's something fundamental that I missed at some point.

function draw() {
    var canvas = document.getElementById('canvas');
    if (canvas.getContext) {
        var ctx = canvas.getContext('2d');

        ctx.beginPath();
        ctx.moveTo(75, 50);
        ctx.lineTo(100, 75);
        ctx.lineTo(100, 25);
        ctx.fill();
    }
}

Here's the fiddle

Answer 1

You forgot to call draw function. Take a look here.

draw();

code looks like this

function draw() {
  var canvas = document.getElementById('canvas');
  if (canvas.getContext){
    var ctx = canvas.getContext('2d');

    ctx.beginPath(); 
    ctx.moveTo(75,50);
    ctx.lineTo(100,75);
    ctx.lineTo(100,25);
    ctx.fill();
  }
}
draw();