Is it possible to iterate through two lists at the same time in Underscore.js?
functional-programming, underscore.js
Solution
Use zip (also from underscore.js) for that. Something like this:
var a = [1, 2, 3];
var b = [4, 5, 6];
var zipped = _.zip(a, b);
// This gives you:
// zipped = [[1, 4], [2, 5], [3, 6]]
var c = _.map(zipped, function(pair) {
var first = pair[0];
var second = pair[1];
return first + second;
});
// This gives you:
// c = [5, 7, 9]
Working example:
- http://jsfiddle.net/beRAD/
Problem
I basically want to express the following behavior using `_.each()` or `_.map()` in Underscore.js. ``` a = [1, 2, 3] b = [3, 2, 1] # Result list c = [0, 0, 0] for i in [0 .. a.length - 1] c[i] = a[i] + b[i] ``` This is definitely possible in Matlab (my primary language) as such: ``` c = arrayfun(@(x,y) x+y, a, b) ``` Intuitively, it feels like the syntax in Underscore should be: ``` c = _.map(a, b, function(x, y){ return x + y;}) ``` However, that argument list isn't acceptable; the second parameter is supposed to be a callable function. The optional "context" argument won't help me in this situation.