The best way to interpolate 2D angles

angleLerp.js

/*
2D Angle Interpolation (shortest distance)

Parameters:
a0 = start angle
a1 = end angle
t = interpolation factor (0.0=start, 1.0=end)

Benefits:
1. Angles do NOT need to be normalized.
2. Implementation is portable, regardless of how the modulo "%" operator outputs sign (i.e. Python, Ruby, Javascript)
3. Very easy to remember.

Thanks to Trey Wilson for the closed-form solution for shortAngleDist!
*/

function shortAngleDist(a0,a1) {
    var max = Math.PI*2;
    var da = (a1 - a0) % max;
    return 2*da % max - da;
}

function angleLerp(a0,a1,t) {
    return a0 + shortAngleDist(a0,a1)*t;
}