CODEWITHSUNDEEP
javascriptlodash
core
core

Reputation: 33079

lodash: mapping array to object

Is there a built-in lodash function to take this:

var params = [
    { name: 'foo', input: 'bar' },
    { name: 'baz', input: 'zle' }
];

And output this:

var output = {
    foo: 'bar',
    baz: 'zle'
};

Right now I'm just using Array.prototype.reduce():

function toHash(array, keyName, valueName) {
    return array.reduce(function(dictionary, next) {
        dictionary[next[keyName]] = next[valueName];
        return dictionary;
    }, {});
}

toHash(params, 'name', 'input');

Wondering if there's a lodash short-cut.

Upvotes: 155

Views: 231391

Answers (8)

djechlin
djechlin

Reputation: 60768

This is probably more verbose than you want, but you're asking for a slightly complex operation so actual code might be involved (the horror).

My recommendation, with zipObject that's pretty logical:

_.zipObject(_.map(params, 'name'), _.map(params, 'input'));

Another option, more hacky, using fromPairs:

_.fromPairs(_.map(params, function(val) { return [val['name'], val['input']));

The anonymous function shows the hackiness -- I don't believe JS guarantees order of elements in object iteration, so callling .values() won't do.

Upvotes: 15

stasovlas
stasovlas

Reputation: 7416

Another way with lodash 4.17.2 

_.chain(params)
    .keyBy('name')
    .mapValues('input')
    .value();

or

_.mapValues(_.keyBy(params, 'name'), 'input')

or with _.reduce

_.reduce(
    params,
    (acc, { name, input }) => ({ ...acc, [name]: input }),
    {}
)

Upvotes: 210

RainedColony
RainedColony

Reputation: 261

This seems like a job for Object.assign:

const output = Object.assign({}, ...params.map(p => ({[p.name]: p.input})));

Edited to wrap as a function similar to OP's, this would be:

const toHash = (array, keyName, valueName) => 
    Object.assign({}, ...array.map(o => ({[o[keyName]]: o[valueName]})));

(Thanks to Ben Steward, good thinking...)

Upvotes: 26

Zeeshan Afzal Satti
Zeeshan Afzal Satti

Reputation: 440

It can also solve without using any lodash function like this: 

let paramsVal = [
    { name: 'foo', input: 'bar' },
    { name: 'baz', input: 'zle' }
];
let output = {};

paramsVal.forEach(({name, input})=>{
  output[name] = input;
})


console.log(output);

enter image description here

Upvotes: 7

Faisal Hasnain
Faisal Hasnain

Reputation: 485

You can use one liner javascript with array reduce method and ES6 destructuring to convert array of key value pairs to object.

arr.reduce((map, { name, input }) => ({ ...map, [name]: input }), {});

Upvotes: 12

Koushik Chatterjee
Koushik Chatterjee

Reputation: 4175

Another way with lodash

creating pairs, and then either construct a object or ES6 Map easily

_(params).map(v=>[v.name, v.input]).fromPairs().value()

or

_.fromPairs(params.map(v=>[v.name, v.input]))

Here is a working example

var params = [
    { name: 'foo', input: 'bar' },
    { name: 'baz', input: 'zle' }
];

var obj = _(params).map(v=>[v.name, v.input]).fromPairs().value();

console.log(obj);
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.js"></script>

Upvotes: 7

danday74
danday74

Reputation: 56996

You should be using _.keyBy to easily convert an array to an object.

Docs here

Example usage below:

var params = [
    { name: 'foo', input: 'bar' },
    { name: 'baz', input: 'zle' }
];
console.log(_.keyBy(params, 'name'));
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.min.js"></script>

If required, you can manipulate the array before using _.keyBy or the object after using _.keyBy to get the exact desired result.

Upvotes: 97

Jagdish Idhate
Jagdish Idhate

Reputation: 7742

Yep it is here, using _.reduce

var params = [
    { name: 'foo', input: 'bar' },
    { name: 'baz', input: 'zle' }
];

_.reduce(params , function(obj,param) {
 obj[param.name] = param.input
 return obj;
}, {});

Upvotes: 44

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