javascript map function accepting multiple array as arguments

Question

How would a js function like this be written?

map(add, [1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12])
 => [15, 18, 21, 24]

I'm trying to write a native js version of the clojure map function

(map + [1 2 3] [4 5 6])
=> [5 7 9]

where map accepts a function and any arbitrary number of arrays after that

With JavaScript code. Explain what you actually want, and what you've tried. — Ian
– Ian, Commented Nov 20, 2013 at 23:19
Are you asking how to write a varargs function in JavaScript? — Reinstate Monica -- notmaynard
– Reinstate Monica -- notmaynard, Commented Nov 20, 2013 at 23:21
Array#reduce may be best here. Something like [[1,2,3,4],[5,6,7,8],[9,10,11,12]].reduce(function(a,b) {return b.map(function(_,i) {return (a[i]||0)+b[i];});},[]); should do it. — Niet the Dark Absol
– Niet the Dark Absol, Commented Nov 20, 2013 at 23:24
That's not map, but zipWith sum what you are looking for — Bergi
– Bergi, Commented Nov 20, 2013 at 23:37

georg · Accepted Answer · 2013-11-21 08:50:39Z

2

Something like

pythonic_map = function(fun) {
    var args = [].slice.call(arguments, 1)
    return args[0].map(function(_, i) {
        return fun.apply(null, args.map(function(x) { return x[i] }));
    });
}

Example:

function add(a, b, c) {
    return a + b + c
}

z = pythonic_map(add, [1, 2, 3, 4], [5, 6, 7, 8], [9, 10, 11, 12])
console.log(z) // [15,18,21,24]

This uses the length of the first argument, to use the shortest/longest argument:

pythonic_map = function(fun) {
    var args = [].slice.call(arguments, 1);
    return args.reduce(function(m, x) {
        return (x.length < m.length) ? x : m; // or > for the longest
    }).map(function(_, i) {
        return fun.apply(null, args.map(function(x) { return x[i] }));
    });
}

edited Nov 21, 2013 at 8:50

answered Nov 20, 2013 at 23:36

georg

216k57 gold badges324 silver badges401 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Ahmed Fasih Over a year ago

I'm surprised the idea of mapping a multi-argument function over multiple arrays is so foreign to Javascript.

Collectives™ on Stack Overflow

javascript map function accepting multiple array as arguments

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related