How to append objects to a key inside JS array?

Question

I have this array :

var res_data = [
 {"id": "1", "text": "AAA", "category": "food", "value": "1"},
 {"id": "2", "text": "BBB", "category": "food", "value": "2"},
 {"id": "3", "text": "CCC", "category": "drinks", "value": "3"}
];

I want to get this

{
 "food": [
 {
 "id": "1",
 "text": "AAA",
 "category": "food",
 "value": "1"
 },
 {
 "id": "2",
 "text": "BBB",
 "category": "food",
 "value": "2"
 }
 ],
 "drinks": [
 {
 "id": "3",
 "text": "CCC",
 "category": "drinks",
 "value": "3"
 }
 ]
}

I've tried to do so by iterating and set the "category" value - as a key , inside a new array, like this :

 var res = [];
 $.each(obj, function () {
 if (this.hasOwnProperty("category")) {
 res[this['category']] = this;
 console.log(this['category']);
 }
 })

but the "food" index is keep overriding....

 drinks:{id: "3", text: "CCC", category: "drinks", value: "3"}
 food: {id: "3", text: "CCC", category: "food", value: "2"}

• brk: append mean what?.The expected output is wrong
• Narendra Jadhav: I think your expected output should be drinks=[{id: "1", text: "AAA", category: "drinks", value: "3"}] food=[{id: "2", text: "BBB", category: "food", value: "2"}, {id: "3", text: "CCC", category: "food", value: "2"}].
• RoyBarOn: Hey, thanks, i want to map the object by categroy, and to create a new object with the correct values...
• RoyBarOn: @NarendraJadhav - YEAH , that's what i'm looking for

Answer 1

A common iteration technique when converting an array into another structure is to use reduction:

const arr = [
 {"id": "1", "text": "AAA", "category": "food", "value": "1"},
 {"id": "2", "text": "BBB", "category": "food", "value": "2"},
 {"id": "3", "text": "CCC", "category": "drinks", "value": "3"}
]
const result = arr.reduce((hash, item) => {
 if (!hash.hasOwnProperty(item.category)) {
 hash[item.category] = []
 }
 hash[item.category].push(item)
 return hash
}, {})
console.log(result)

Answer 2

You can also use forEach for array.

ES5

var arr = [{
 "id": "1",
 "text": "AAA",
 "category": "food",
 "value": "1"
 },
 {
 "id": "2",
 "text": "BBB",
 "category": "food",
 "value": "2"
 },
 {
 "id": "3",
 "text": "CCC",
 "category": "drinks",
 "value": "3"
 }
 ],
 outpt = {};
arr.forEach(function(item) {
 if (!outpt.hasOwnProperty(item.category)) {
 outpt[item.category] = []
 }
 outpt[item.category].push(item)
});
console.log(outpt)

ES6

let arr = [{
 "id": "1",
 "text": "AAA",
 "category": "food",
 "value": "1"
 },
 {
 "id": "2",
 "text": "BBB",
 "category": "food",
 "value": "2"
 },
 {
 "id": "3",
 "text": "CCC",
 "category": "drinks",
 "value": "3"
 }
 ],
 outpt = {};
arr.forEach((item) => {
 if (!outpt.hasOwnProperty(item.category)) {
 outpt[item.category] = []
 }
 outpt[item.category].push(item)
});
console.log(outpt)

Answer 3

var res_data = [
 {"id": "1", "text": "AAA", "category": "food", "value": "1"},
 {"id": "2", "text": "BBB", "category": "food", "value": "2"},
 {"id": "3", "text": "CCC", "category": "drinks", "value": "3"}
];
var result = {};
for(var i = 0; i < res_data.length; i++){
 if(result[res_data[i].category] == undefined)
 result[res_data[i].category] = [];
 result[res_data[i].category].push(res_data[i])
}
console.log(result)

Answer 4

Assuming a valid output, you can use the function reduce.

var data = [ {"id": "1", "text": "AAA", "category": "food", "value": "1"}, {"id": "2", "text": "BBB", "category": "food", "value": "2"}, {"id": "3", "text": "CCC", "category": "drinks", "value": "3"}],
 result = data.reduce((a, c) => {
 (a[c.category] || (a[c.category] = [])).push(c);
 return a;
 }, {});
console.log(result);

Answer 5

Try this:

var res_data = [
 {"id": "1", "text": "AAA", "category": "food", "value": "1"},
 {"id": "2", "text": "BBB", "category": "food", "value": "2"},
 {"id": "3", "text": "CCC", "category": "drinks", "value": "3"}
];
function filter(arr, key, value) {
 var res = [];
 for(var x = 0, max = arr.length; x < max; x = x + 1) {
 if(typeof arr[x] === 'object' && arr[x].hasOwnProperty(key) && arr[x][key] === value) {
 res.push(arr[x]);
 }
 }
 return res;
}

Then you can filter by any property like this:

filter(res_data, 'category', 'food');

It will return:

[
 {"id": "1", "text": "AAA", "category": "food", "value": "1"},
 {"id": "2", "text": "BBB", "category": "food", "value": "2"}
]