Vector2.angle() performance

[gonnavis]

I'm not sure whether the performance is better.
But in glsl, I heard "the less conditional the better".
Test result can check http://glslsandbox.com/e#61015.59 .

[gonnavis]

OK, I tested in my own chrome console with these code:
First define the two angle functions, angle for current, angle2 for new.

function angle(x,y){
    var angle = Math.atan2( y, x );

    if ( angle < 0 ) angle += 2 * Math.PI;

    return angle;
}
function angle2(x,y){
    var angle = Math.atan2( - y, - x ) + Math.PI;

    return angle;
}

And then run these two functions in console 1000000000 times seperately.

var start=performance.now()
for(let i=0;i<1000000000;i++){
	angle(1,1)
}
console.log(performance.now()-start)

var start=performance.now()
for(let i=0;i<1000000000;i++){
	angle2(1,1)
}
console.log(performance.now()-start)

With angle, I got an average time 1330ms.
With angle2, I got an average time 560ms.
So I think it's a big performance improvement.

[mrdoob]

Thanks!