versatile JavaScript "zip" function. Works with objects, arrays, and yep - even strings.

zip.js

function zip(a, b) {
  var arr = [];
  for (var key in a) arr.push([a[key], b[key]]);
  return arr;
}

console.log(zip('foo', 'bar'));
//=> [ [ 'f', 'b' ], [ 'o', 'a' ], [ 'o', 'r' ] ]

console.log(zip(['a', 'b', 'c'], ['x', 'y', 'z']));
//=> [ [ 'a', 'x' ], [ 'b', 'y' ], [ 'c', 'z' ] ]

var obj1 = {a: 'aaa', b: 'bbb', c: 'ccc'};
var obj2 = {a: 'xxx', b: 'yyy', c: 'zzz'};
var obj3 = {x: 'xxx', y: 'yyy', z: 'zzz'};

console.log(zip(obj1, obj2));
//=> [ [ 'aaa', 'xxx' ], [ 'bbb', 'yyy' ], [ 'ccc', 'zzz' ] ]

console.log(zip(Object.keys(obj1), Object.keys(obj3)));
//=> [ [ 'a', 'x' ], [ 'b', 'y' ], [ 'c', 'z' ] ]

Using for...in for arrays and strings is not a good practice, considering the order of enumeration is undefined. Here is a better implementation using iterators:

function* zip(...args) {
	const iterators = args.map(x => x[Symbol.iterator]());
	while (true) {
		const current = iterators.map(x => x.next());
		if (current.some(x => x.done)) {
			break;
		}
		yield current.map(x => x.value);
	}
}

console.log([...zip("ABCD", "ABCD", "AB")])
console.log([...zip([1, 2, 3], [1, 2, 3])])
console.log([...zip([], [])])

It works with any number of iterable arguments and they don't have to be the same length 😺

The solution by @brokenpylons is nice, but if I am not mistaken it will run endlessly when called with an empty set of arguments?
current.some(…) on an empty array always returns false, hence the break condition is never reached on args === []

It should be solvable by

while(iterators.length) {…}