Easy Noise

HTML

<canvas id='canvas'></canvas>

JavaScript

function randInt(low, high) {
    return ~~(Math.random() * (high - low)) + low;
}

var size = 100;
var map = [];
for (var i = 0; i < size; i++) {
    map.push([]);
    for (var j = 0; j < size; j++) {
        map[i].push(0);
    }
}

for (var i = 0; i < size; i++) {
    for (var j = 0; j < size; j++) {
        map[i][j] = randInt(0, 255);
    }
}

var Renderer = {
    canvas: null,
    ctx: null,
    size: 512,
    scale: 0,
    Initialize: function () {
        this.canvas = document.getElementById('canvas');
        this.canvas.width = this.size;
        this.canvas.height = this.size;
        this.ctx = canvas.getContext('2d');
        this.scale = this.canvas.width / size;
    },
    Update: function () {
        for (var y = 0; y < size; y++) {
            for (var x = 0; x < size; x++) {
                var tile = map[x][y];
                var color = 'rgb(' + tile + ',' + tile + ',' + tile + ')';
                this.ctx.fillStyle = color;
                this.ctx.fillRect(x * this.scale, y * this.scale, this.scale, this.scale);
            }
        }
    }
};

Renderer.Initialize();
Renderer.Update();