arrayIntersection.js

// arrayIntersection.js v1
function arrayIntersection(arrayA, arrayB) {
	let newArray = [];
	for (let i = 0; i < arrayA.length; i++) {
		if (arrayB.indexOf(arrayA[i]) > -1) {
			newArray.push(arrayA[i]);
		};
	};
	return newArray;
};
Array.prototype.intersection = function(arrayB) {
	return arrayIntersection(this, arrayB);
};

arrayIntersection.min.js

// arrayIntersection.min.js v1
function arrayIntersection(a,b){let c=[];for(let d=0;d<a.length;d++)-1<b.indexOf(a[d])&&c.push(a[d]);return c}Array.prototype.intersection=function(a){return arrayIntersection(this,a)};