how to iterate over nested array object in javascript

Question

I would like to know how to iterate through a nested array of objects in Javascipt? I have a sample object named obj. I want to retrieve the object based on condition 'in' is 'string' and 'out' 'number'.

// tried got stuck
const output = [];
 myList.forEach(entry => {
 Object.keys(entry).forEach(key => {
 const entity = entry[key][0];
 if (entity.in === "string" && entity.out === "number") {
 output.push(entity);
 }
 });
 });

var obj = [{
 "ston": [{
 "id": "identity1",
 "in": "string",
 "out": "number",
 "value": 10
 },{
 "id": "identity2",
 "in": "string",
 "out": "number",
 "value": 10
 }],
 "nton": [{
 "id": "identity1",
 "in": "number",
 "out": "number",
 "value": 20
 },{
 "id": "identity2",
 "in": "number",
 "out": "number",
 "value": 30
 }]
 }]

Expected Output

 [{
 "id": "identity1",
 "in": "string",
 "out": "number",
 "value": 10
 },{
 "id": "identity2",
 "in": "string",
 "out": "number",
 "value": 10
 }]

Answer 1

You can use rebuild that object to a nested array then flatten and finally filter.

var obj = [
 {
 "ston": [
 {"id": "identity1", "in": "string", "out": "number", "value": 10},
 {"id": "identity2", "in": "string", "out": "number", "value": 10}
 ],
 "nton": [
 {"id": "identity1", "in": "number", "out": "number", "value": 20},
 {"id": "identity2", "in": "number", "out": "number", "value": 30}
 ]
 }
];
const tmp = obj.map(e => Object.entries(e).map(([k, v]) => v)).flat(3)
const rs = tmp.filter(e => e.out==='number' && e.in ==='string')
console.log(rs)

Answer 2

Simple recursive function:

var obj = [{
 "ston": [{
 "id": "identity1",
 "in": "string",
 "out": "number",
 "value": 10
 }, {
 "id": "identity2",
 "in": "string",
 "out": "number",
 "value": 10
 }],
 "nton": [{
 "id": "identity1",
 "in": "number",
 "out": "number",
 "value": 20
 }, {
 "id": "identity2",
 "in": "number",
 "out": "number",
 "value": 30
 }]
}];
function getObjects(inVal, outVal) {
 var matches = [];
 obj.forEach(child => {
 Object.values(child).forEach(arr => {
 if (arr.some(e => e.in == inVal && e.out == outVal)) {
 matches.push([...arr.filter(e => e => e.in == inVal && e.out == outVal)]);
 }
 });
 });
 return matches.flat();
}
console.log(getObjects("string", "number"));

Answer 3

Here you have one solution that uses mainly Array.reduce() to iterate over the outter objects of the array, get a flattened array of the values from every outter object to create an array with inner objects and then filter those meeting the condition while saving they in a new array:

var obj = [
 {
 "ston": [
 {"id": "identity1", "in": "string", "out": "number", "value": 10},
 {"id": "identity2", "in": "string", "out": "number", "value": 10}
 ],
 "nton": [
 {"id": "identity1", "in": "number", "out": "number", "value": 20},
 {"id": "identity2", "in": "number", "out": "number", "value": 30}
 ]
 }
];
let res = obj.reduce((acc, o) =>
{
 acc = acc.concat(Object.values(o).flat().filter(
 o => o.in === "string" && o.out === "number"
 ));
 return acc;
}, []);
console.log(res);

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Other documentation of used methods:

• Array.concat()
• Array.flat()
• Array.filter()
• Object.values()

Or, after some time thinking, you can use the next simplified version with Array.map()

var obj = [
 {
 "ston": [
 {"id": "identity1", "in": "string", "out": "number", "value": 10},
 {"id": "identity2", "in": "string", "out": "number", "value": 10}
 ],
 "nton": [
 {"id": "identity1", "in": "number", "out": "number", "value": 20},
 {"id": "identity2", "in": "number", "out": "number", "value": 30}
 ]
 }
];
let res = obj.map(Object.values).flat(2).filter(
 o => o.in === "string" && o.out === "number"
);
console.log(res);

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