function length$3(a) {
    var x = a[0];
    var y = a[1];
    var z = a[2];
    var w = a[3];
    return Math.hypot(x, y, z, w);
  }
Calculates the length of a vec4

@param {ReadonlyVec4} a vector to calculate length of
@returns {Number} length of a