Convert Array to Object

Question

What is the best way to convert:

['a','b','c']

to:

{
  0: 'a',
  1: 'b',
  2: 'c'
}

Answer 1

Using javascript#forEach one can do this

var result = {},
    attributes = ['a', 'b','c'];

attributes.forEach(function(prop,index) {
  result[index] = prop;
});

With ECMA6:

attributes.forEach((prop,index)=>result[index] = prop);

Answer 2

let i = 0;
let myArray = ["first", "second", "third", "fourth"];

const arrayToObject = (arr) =>
    Object.assign({}, ...arr.map(item => ({[i++]: item})));

console.log(arrayToObject(myArray));

Or use

myArray = ["first", "second", "third", "fourth"]
console.log({...myArray})

Answer 3

I have faced this issue multiple times and decided to write a function that is as generic as possible. Have a look and feel free to modify anything

function typeOf(obj) {
    if ( typeof(obj) == 'object' ) {
        if (obj.length)
            return 'array';
        else
            return 'object';
    } else
    return typeof(obj);
}

function objToArray(obj, ignoreKeys) {
    var arr = [];
    if (typeOf(obj) == 'object') {
        for (var key in obj) {
            if (typeOf(obj[key]) == 'object') {
                if (ignoreKeys)
                    arr.push(objToArray(obj[key],ignoreKeys));
                else
                    arr.push([key,objToArray(obj[key])]);
            }
            else
                arr.push(obj[key]);
        }
    }else if (typeOf(obj) == 'array') {
        for (var key=0;key<obj.length;key++) {
            if (typeOf(obj[key]) == 'object')
                arr.push(objToArray(obj[key]));
            else
                arr.push(obj[key]);
        }
    }
    return arr;
}

Answer 4

Five years later, there's a good way :)

Object.assign was introduced in ECMAScript 2015.

Object.assign({}, ['a', 'b', 'c'])
// {'0':'a', '1':'b', '2':'c'}

Answer 5

This allows you to generate from an array an object with keys you define in the order you want them.

Array.prototype.toObject = function(keys){
    var obj = {};
    var tmp = this; // we want the original array intact.
    if(keys.length == this.length){
        var c = this.length-1;
        while( c>=0 ){
            obj[ keys[ c ] ] = tmp[c];
            c--;
        }
    }
    return obj;
};

result = ["cheese","paint",14,8].toObject([0,"onion",4,99]);

console.log(">>> :" + result.onion); will output "paint", the function has to have arrays of equal length or you get an empty object.

Here is an updated method

Array.prototype.toObject = function(keys){
    var obj = {};
    if( keys.length == this.length)
        while( keys.length )
            obj[ keys.pop() ] = this[ keys.length ];
    return obj;
};

Answer 6

If you can use Map or Object.assign, it's very easy.

Create an array:

const languages = ['css', 'javascript', 'php', 'html'];

The below creates an object with index as keys:

Object.assign({}, languages)

Replicate the same as above with Maps

Converts to an index based object {0 : 'css'} etc...

const indexMap = new Map(languages.map((name, i) => [i, name] ));
indexMap.get(1) // javascript

Convert to an value based object {css : 'css is great'} etc...

const valueMap = new Map(languages.map(name => [name, `${name} is great!`] ));
valueMap.get('css') // css is great