Merge keys array and values array into an object in JavaScript

Question

I have:

var keys = [ "height", "width" ];
var values = [ "12px", "24px" ];

And I'd like to convert it into this object:

{ height: "12px", width: "24px" }

In Python, there's the simple idiom dict(zip(keys,values)) . Is there something similar in jQuery or plain JavaScript, or do I have to do this the long way?

Answer 1

The simplest ES6 one-liner solution using Array reduce :

const keys = ['height', 'width'];
const values = ['12px', '24px'];
const merged = keys.reduce((obj, key, index) => ({ ...obj, [key]: values[index] }), {});

Answer 2

Simple JS function would be:

function toObject(names, values) {
    var result = {};
    for (var i = 0; i < names.length; i++)
         result[names[i]] = values[i];
    return result;
}

Of course you could also actually implement functions like zip, etc as JS supports higher order types which make these functional-language-isms easy:D

Answer 3

use lodash.

_.zipObject

Example

_.zipObject(['a', 'b'], [1, 2]);
// ➜ { 'a': 1, 'b': 2 }

Answer 4

As an alternate solution, not already mentioned I think:

  var result = {};
  keys.forEach((key, idx) => result[key] = values[idx]);

Answer 5

You can combine two arrays with map method, then convert it with Object.fromEntries .

 var keys = ["height", "width"]; var values = ["12px", "24px"]; var array = keys.map((el, i) => { return [keys[i], values[i]]; }); // → [["height", "12px"], ["width", "24px"]] var output = Object.fromEntries(array); // → {height: "12px", width: "24px"} console.log(output);

Answer 6

A functional approach with immutability in mind:

 const zipObj = xs => ys => xs.reduce( (obj, x, i) => ({...obj, [x]: ys[i] }), {}) const arr1 = ['a', 'b', 'c', 'd'] const arr2 = ['e', 'f', 'g', 'h'] const obj = zipObj (arr1) (arr2) console.log (obj)

Answer 7

You could use a reduce() function to map the key-value pairs to an object.

 /** * Apply to an existing or new object, parallel arrays of key-value pairs. * * @param {string[]} keys - List of keys corresponding to their accociated values. * @param {object[]} vals - List of values corresponding to their accociated keys. * @param {object} [ref={}] - Optional reference to an existing object to apply to. * * @returns {object} - The modified or new object with the new key-value pairs applied. */ function toObject(keys, vals, ref) { return keys.length === vals.length? keys.reduce(function(obj, key, index) { obj[key] = vals[index]; return obj; }, ref || {}): null; } var keys = [ "height", "width" ]; var values = [ "12px", "24px" ]; document.body.innerHTML = '<pre>' + JSON.stringify(toObject(keys, values), null, 2) + '</pre>';

Answer 8

Now we have Object.fromEntries we can do something like that:

 const keys = [ "height", "width" ]; const values = [ "12px", "24px" ]; const myObject = Object.fromEntries( values.map((value, index) => [keys[index], value]) ); console.log(myObject);

Answer 9

You could transpose the arrays and get the object with the entries.

 const transpose = (r, a) => a.map((v, i) => [...(r[i] || []), v]), keys = [ "height", "width" ], values = [ "12px", "24px" ], result = Object.fromEntries([keys, values].reduce(transpose, [])); console.log(result);

Answer 10

Here's an example with all consts (non-modifying) and no libraries.

 const keys = ["Adam", "Betty", "Charles"]; const values = [50, 1, 90]; const obj = keys.reduce((acc, key, i) => { acc[key] = values[i]; return acc; }, {}); console.log(obj);

Alternatively, if you'd consider libraries you could use lodash zipobject which does just what you asked.

Answer 11

function combineObject( keys, values)
{
    var obj = {};
    if ( keys.length != values.length)
       return null;
    for (var index in keys)
        obj[keys[index]] = values[index];
     return obj;
};


var your_obj = combine( your_keys, your_values);

Answer 12

Here's one which will transform nested arrays into an array of multiple key-value objects.

 var keys = [ ['#000000', '#FFFFFF'], ['#FFFF00', '#00FF00', '#00FFFF', '#0000FF'], ]; var values = [ ['Black', 'White'], ['Yellow', 'Green', 'Cyan', 'Blue'], ]; const zipObj = xs => ys => xs.reduce( (obj, x, i) => ({...obj, [x]: ys[i] }), {}) var array = keys.map((el, i) => zipObj (keys[i]) (values[i])); console.log(array);

Output is

[
  {
    "#000000": "Black",
    "#FFFFFF": "White"
  },
  {
    "#FFFF00": "Yellow",
    "#00FF00": "Green",
    "#00FFFF": "Cyan",
    "#0000FF": "Blue"
  }
]

Answer 13

Providing a solution with a for...of loop.

 var keys = ["height", "width"]; var values = ["12px", "24px"]; const result = {}; for (let [index, key] of keys.entries()) result[key] = values[index]; console.log(result);

You can also use a library like ramda which has zipObj function. Example:

 const keys = ["height", "width"]; const values = ["12px", "24px"]; const result = R.zipObj(keys, values); console.log(result);

Answer 14

In the jQuery-Utils project , the ArrayUtils module has a zip function implemented.

//...
zip: function(object, object2, iterator) {
    var output = [];
    var iterator = iterator || dummy;
        $.each(object, function(idx, i){
        if (object2[idx]) { output.push([i, object2[idx]]); }
    });
    return output;
}
//...