With the arrival of ES6 with sets and splat operator (at the time of being works only in Firefox, check compatibility table), you can write the following one liner:
var a = ['a', 'b', 'c', 'd']; var b = ['a', 'b']; var b1 = new Set(b); var difference = [...new Set(a.filter(x => !b1.has(x)))]; which will result in [ "c", "d" ].
