JavaScript: Functional mapping?

Is there a more succinct way to write this?

var me = {};

for (var i in you) {
 me[i] = you[i];
}

(where you is an arbi开发者_如何学Ctrarily-lengthed JavaScript array)

In other words, given the input of:

var you = [
 "what",
 "r",
 "u"
];

The output, me, becomes:

me = {
 0: "what",
 1: "r",
 2: "u"
};

Like, a one-liner that uses some functional method?

Why do you want to do this? Arrays in JavaScript are Objects, except with some additional properties like slice, splice, push and length.

Internally, Arrays and Objects are stored exactly in the same way: e.g. array[0] is the same as array["0"], or object["0"] (unlike in other languages where adjacent array indices are in fact in adjacent memory - array "indices" are simply converted into strings in JavaScript).

So, if you just want to copy the data, then this will suffice:

me = you.slice(); // me is a copy of you, but is still an array

Or, if you really want some sort of mapping functionality, then underscore.js provides a whole collection of functional programming tools for your perusal.

There is no built-in function that does what you ask, however some of the widely used javascript libraries like jQuery provide such a function. In jQuery's case: jQuery.extend()

Usage:

var me = {};
jQuery.extend(me,someObject);

//or, equivalently -
var me2 = jQuery.extend({},someObject);

jQuery has an extend() function (documentation here). Your code would look like this:

var me = {};
var you = ["what", "r", "u"];
$.extend(me, you);

This would allow you to do things like:

alert("Second element: " + me[1]);

It's a little odd, but I think it's what you're looking for.

I saw what you were trying to achieve with your string formatter. Instead of answering your original question of coming up with a concise implementation of one portion of it, I'll suggest a concise (and more flexible) implementation for the whole thing:

String.prototype.format = function () {
    var args = arguments;

    return this.replace(/\{(?:(\d+)|(\w+))\}/g, function (s, idx, prop) {
        return prop && args[0]
            ? args[0][prop]
            : args[idx];
    });
};

When you have a number n inside a token "{n}", it uses the n-th argument for replacement. Otherwise, for non-numerical keys, it picks the corresponding property of the first argument.

For example:

"I have {1} {name}s in my basket.".replace({ type: "fruit", name: "eggplant" }, 4);

Returns:

"I have 4 eggplants in my basket."

The underscore.js library also has a basic extend function.

var me = _({}).extend(you)

or

var me = {}
_(me).extend(you)

or

var me = {}
_.extend(me, you)