gl.Frustr...ATION

Khronos, when will you add glFrustum to WebGL standard?

Never.

You have to do it yourself (calcule the matrix, send it to your projection mat).

function glFrustum(left, right, bottom, top, near, far) {
	var rl = right-left, tb = top-bottom, fn = far-near;
	<webgl context>.uniformMatrix4fv( <webgl projection uniform matrix>, false, Float32Array([
		(near*2) / rl, 0, 0, 0,
		0, (near*2) / tb, 0, 0,
		(right + left) / rl,  (top + bottom) / tb, -(far + near) / fn, -1,
		0, 0, -(far*near*2) / fn, 0
	]); );
};

I recommend you to use an existent matrix library in javascript (since I think you don’t want to build your own).