Conversion object into array of objects

Question

I am trying to combine these two object array into one object array with combining each property with their own values.

var a ={'a':[1,2,3,4],'b':[2,3,4,5]}

to [{'a':1,'b':2},{'a':2,'b':3},{'a':3,'b':4},{'a':4,'b':5}]

How can I achieve this using lodash library?

Please don't ask for solutions without trying to solve the problem yourself first. If you have tried something, please share in your question what it is that you have tried. — Cal Irvine
– Cal Irvine, Commented Sep 10, 2019 at 15:02
I checked all the default lodash methods if any are there but couldnt find.. — Sourabh Slk
– Sourabh Slk, Commented Sep 10, 2019 at 15:02
Checked stackoverflow.com/questions/32100692/… But there the value is not an array so wanted a help how to do it throuh lodash — Sourabh Slk
– Sourabh Slk, Commented Sep 10, 2019 at 15:11
Lodash is a nice little toolbox but you don't necessarily have to use it. This is perfectly doable with a few lines of Javascript. — Jeremy Thille
– Jeremy Thille, Commented Sep 10, 2019 at 15:11

Mr. Polywhirl · Accepted Answer · 2019-09-10 16:20:28Z

You need to iterate over the values for one of the keys, and then for each value—iterate over all the keys. This can be done in pure JavaScript fairly easily.

e.g. [ 1, 2, 3, 4 ] for key a, then loop over they keys: [ 'a', 'b' ]

Note: You will see the parameter '_' (underscore) used as the first parameter for the mapping below. This represents the current value in the list for the value of key 'a'. It is meaningless, but we need to have it there to access the next parameter (index of current value).

// Code Golf - zipObjects (100 bytes)
var z=a=>(x=>a[x[0]].map((_,i)=>x.reduce((o,k)=>Object.assign(o,{[k]:a[k][i]}),{})))(Object.keys(a))

function zipObjects(arr) {
  return (keys => {
    return arr[keys[0]].map((_, valueIndex) => {
      return keys.reduce((obj, key) => {
        return Object.assign(obj, {[key] : arr[key][valueIndex]});
      }, {});
    });
  })(Object.keys(arr));
}

console.log(zipObjects({ 'a': [1, 2, 3, 4], 'b': [2, 3, 4, 5] }));

.as-console-wrapper { top: 0; max-height: 100% !important; }

With lodash

You can declare a plugin function very similarly.

_.mixin({
  'zipObjects' : function(arr) {
    return (keys => {
      return _.map(arr[_.head(keys)], (value, valueIndex) => {
        return _.reduce(keys, (obj, key) => {
          return _.assignIn(obj, {[key] : arr[key][valueIndex]});
        }, {});
      });
    })(_.keys(arr));
  }
});

console.log(_.zipObjects({ 'a': [1, 2, 3, 4], 'b': [2, 3, 4, 5] }));

.as-console-wrapper { top: 0; max-height: 100% !important; }

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.15/lodash.core.min.js"></script>

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