If you want to map objects to something (in this case a property). I think Array.prototype.map is what you're looking for if you want to code functionally.

(fiddle)

If you want to support older browsers, that are not ES5 compliant you can shim it (there is a polyfill on the MDN page above). Another alternative would be to use underscorejs's pluck method:

var users = [
      {name: "Joe", age: 22},
      {name: "Kevin", age: 24},
      {name: "Peter", age: 21}
    ];
var result = _.pluck(users,'name').join(",")

Two one-liners:

with lodash:

res = _(json1).concat(json2).groupBy('id').map(_.spread(_.assign)).value();

in ES2015:

res = json2.map(x => Object.assign(x, json1.find(y => y.id == x.id)));

You can do it like this -

let arr1 = [
    { id: "abdc4051", date: "2017-01-24" },
    { id: "abdc4052", date: "2017-01-22" }
];

let arr2 = [
    { id: "abdc4051", name: "ab" },
    { id: "abdc4052", name: "abc" }
];

let arr3 = arr1.map((item, i) => Object.assign({}, item, arr2[i]));

console.log(arr3);

Use below code if arr1 and arr2 are in a different order:

let arr1 = [
  { id: "abdc4051", date: "2017-01-24" }, 
  { id: "abdc4052", date: "2017-01-22" }
];

let arr2 = [
  { id: "abdc4051", name: "ab" },
  { id: "abdc4052", name: "abc" }
];

let merged = [];

for(let i=0; i<arr1.length; i++) {
  merged.push({
   ...arr1[i], 
   ...(arr2.find((itmInner) => itmInner.id === arr1[i].id))}
  );
}

console.log(merged);

Use this if arr1 and arr2 are in a same order

let arr1 = [
  { id: "abdc4051", date: "2017-01-24" }, 
  { id: "abdc4052", date: "2017-01-22" }
];

let arr2 = [
  { id: "abdc4051", name: "ab" },
  { id: "abdc4052", name: "abc" }
];

let merged = [];

for(let i=0; i<arr1.length; i++) {
  merged.push({
   ...arr1[i], 
   ...arr2[i]
  });
}

console.log(merged);

Try using jQuery.map() - Array.map() not used because of IE < 9 support

For JSON.stringify() - use json2 for old browser support

$.map(array, function(obj){return JSON.stringify(obj)}).join(' ')

Update: To get the value properties

var string = $.map(array, function(obj){
    return obj.value
}).join(' ');

Demo: Fiddle

You can use Array.prototype.reduce:

const members = [
  {
    groupId: 1,
    name: 'test group',
    userId: 2,
    first_name: 'Ross',
    last_name: 'Geller',
    joinedDate: "2022-01-13T13:25:43.510Z",
    leftDate: "2023-02-24T19:07:11.110Z"   
  },
  {
    groupId: 12,
    name: 'test group 2',
    userId: 2,
    first_name: 'Ross',
    last_name: 'Geller',
    joinedDate: "2022-01-13T00:00:00.000Z",
    leftDate: null
  },
  {
    groupId: 12,
    name: 'test group 2',
    userId: 6,
    first_name: 'Joey',
    last_name: 'Tribbiani',
    joinedDate: "2022-01-13T00:00:00.000Z",
    leftDate: null
  }
];

const grouped = members.reduce((acc, { groupId, name, ...member }) => {
  const existingGroup = acc.find(group => group.groupId === groupId);
  if (existingGroup)
    existingGroup.members.push(member);
  else
    acc.push({
      groupId,
      name,
      members: [
        member
      ]
    });
  return acc;
}, []);

console.log(grouped);

Like this?

var combined = [];
function findSecond(id,second){
    for (var i=0;i<second.length;i++){
        if(second[i].id === id){
            return second[i];
        }
    }
    return null
}

while (el = arr1.pop()){
    var getSec = findSecond(el.id,arr2);
    if (getSec){
        for (var l in getSec){
            if (!(l in el)) {
                el[l] = getSec[l];
            }
        }
        combined.push(el);
    }
}

If the arrays have the same length, and the id's are equal, a simpler merge will do:

function merge(a1,a2) {
    var i = -1;
    while ((i = i+1)<a1.length)  {
     for (var l in a2[i]) {
            if (!(l in a1[i] )) {
                a1[i][l] = a2[i][l];
            }
     }
    }
   return a1; 
}

Here's a working example

[Edit 2016/07/30] Added a snippet using more functional approach and, based on @djangos comment, an extra method to combine both arrays.

Show code snippet

(function() {
    var alert = function(str) {document.querySelector('#result').textContent += str + '\n';};
    var arrays = getArrays();
  
    alert('Combine on id (shared id\'s):')
    alert(JSON.stringify(combineById(arrays.arr1, arrays.arr2), null, ' '));
  
    alert('\nCombine on id (all id\'s):')
    alert(JSON.stringify(combineBothById(arrays.arr1, arrays.arr2), null, ' '));
  
    // for combineBothById the parameter order isn't relevant
    alert('\nCombine on id (all id\'s, demo parameter order not relevant):')
    alert(JSON.stringify(combineBothById(arrays.arr2, arrays.arr1), null, ' '));
  
    // combine first array with second on common id's
    function combineById(arr1, arr2) {
      return arr1.map(
          function (el) {
                var findInB = this.filter(function (x) {return x.id === el.id;});
                if (findInB.length) {
                    var current = findInB[0];
                    for (var l in current) {
                        if (!el[l]) {el[l] = current[l];}
                    }
                }
                return el;
          }, arr2);
    }

    // combine first array with second on all id's
    function combineBothById(arr1, arr2) {
        var combined = arr1.map(
            function (el) {
                var findInB = this.filter(function (x) {return x.id === el.id;});
                if (findInB.length) {
                    var current = findInB[0];
                    for (var l in current) {
                        if (!el[l]) {el[l] = current[l];}
                    }
                }
                return el;
            }, arr2);
        combined = combined.concat(arr2.filter(
            function (el) {
                return !this.filter(function (x) {return x.id === el.id;}).length;
            }, combined));
        return combined;
    }
  
    function getArrays() {
        return {
            arr1: [{
                id: 1,
                name: 'fred',
                title: 'boss'
            }, {
                id: 2,
                name: 'jim',
                title: 'nobody'
            }, {
                id: 3,
                name: 'bob',
                title: 'dancer'
            }],
            arr2: [{
                id: 1,
                wage: '300',
                rate: 'day'
            }, {
                id: 2,
                wage: '10',
                rate: 'hour'
            }, {
                id: 4,
                wage: '500',
                rate: 'week'
            }]
        };
    }
}());

<pre id="result"></pre>

A simple reduce on the data can solve this. Often you would use an object to map the values to keys, and then map out the key/values to a new array, but in this case you can just use an index to target a nested array in the returned array instead.

var out = data.reduce(function (p, c) {

  // the key is the first array element, the value the second
  // and i is the index of the nested array in the returned array
  var key = c[0],
      val = c[1],
      i = +key.substr(5) || 0;

  // if the nested array in the returned array doesn't exist
  // create it as a new array with the key as the first element
  p[i] = p[i] || [key];

  // if the value is not null, push it to the correct
  // nested array in the returned array
  if (val) p[i].push(val);
  return p;
}, []);

DEMO