Merge arrays inside an array in javascript

Question

Going through the link Merge/flatten an array of arrays in JavaScript? is somewhat what i need. But with that link and many other links shows merging of arrays of two arrays. What I have is as follows

[
   {
      "setter":[
         {
            "keyname":"Sample Size",
            "cond":"=",
            "value":1
         }
      ]
   },
   {
      "setter":[
         {
            "joinedcond":"and"
         },
         {
            "keyname":"Sample Size",
            "cond":"=",
            "value":2
         }
      ]
   }
]

That is I have an array and inside that array I have an array "setter". What I want is actually merging all setter array as a single array. Having said the merge should produce below output

[
   {
      "setter":[
         {
            "keyname":"Sample Size",
            "cond":"=",
            "value":1
         },
         {
            "joinedcond":"and"
         },
         {
            "keyname":"Sample Size",
            "cond":"=",
            "value":2
         }
      ]
   }
]

Help would be appreciated. Thanks

Do you really need an array for the final output ? Can it not be a simple object with a `setter` property ? — Weedoze, Apr 21 '17 at 06:27
ok no problems ! I provided you a solution to generate an array — Weedoze, Apr 21 '17 at 06:31

score 0 · Accepted Answer · answered Apr 21 '17 at 06:29

0

You can do it by using Array#reduce

var arr = [{"setter":[{"keyname":"Sample Size","cond":"=","value":1}]},{"setter":[{"joinedcond":"and"},{"keyname":"Sample Size","cond":"=","value":2}]}];

var finalArr = arr.reduce((a,x)=>{
  (a[0].setter = a[0].setter || []).push(...x.setter);
  return a;
},[{}]);

console.log(finalArr);

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answered Apr 21 '17 at 06:29

Weedoze

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Thanks man it worked. Want to know couple of things 1) ... exactly inside push does ? 2) Will it be faster ? – Neo Apr 21 '17 at 06:35
@Neo `...` is the spread operator (Check the doc). I am using it inside the `push` function to push all the array instead of looping setter to push each item one by one. Faster compared to what ? – Weedoze Apr 21 '17 at 06:36
Got that... I was actually hoping will it be faster than for loop. But guess the spread operator did the trick, isn't it ? – Neo Apr 21 '17 at 06:39

score 0 · Answer 2 · answered Apr 21 '17 at 06:33

You could use a hash table for the outer keys and concat the inner values with a dynamic approach for the outer keys, like setter.

var data = [{ setter: [{ keyname: "Sample Size", cond: "=", value: 1 }] }, { setter: [{ joinedcond: "and" }, { keyname: "Sample Size", cond: "=", value: 2 }] }],
    result = data.reduce(function (hash) {
        return function (r, o) {
            Object.keys(o).forEach(function (k) {
                if (!hash[k]) {
                    hash[k] = {};
                    r.push(hash[k]);
                }
                hash[k][k] = (hash[k][k] || []).concat(o[k]);
            });
            return r;
        };
    }(Object.create(null)), []);

console.log(result);

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score 0 · Answer 3 · answered Dec 04 '17 at 22:57

Using ES6 Rest and Spread operators we can achieve the same with a recursive function call:

let cdata= data.slice();//Copy the data
let condensedArray=[];

function flatten(data, ...rest){
    let [{ setter }] = data; 
    condensedArray = [...condensedArray, ...setter];
    data.splice(0,1); 
    data.length>0?flatten(data, ...data):console.log('Complete');
}

flatten(cdata, ...cdata);
console.log(condensedArray);

Merge arrays inside an array in javascript

3 Answers3