How would I find all values by specific key in a deep nested object?
For example, if I have an object like this:
const myObj = {
id: 1,
children: [
{
id: 2,
children: [
{
id: 3
}
]
},
{
id: 4,
children: [
{
id: 5,
children: [
{
id: 6,
children: [
{
id: 7,
}
]
}
]
}
]
},
]
}
How would I get an array of all values throughout all nests of this obj by the key of id.
Note: children is a consistent name, and id's won't exist outside of a children object.
So from the obj, I would like to produce an array like this:
const idArray = [1, 2, 3, 4, 5, 6, 7]
This is a bit late but for anyone else finding this, here is a clean, generic recursive function:
function findAllByKey(obj, keyToFind) {
return Object.entries(obj)
.reduce((acc, [key, value]) => (key === keyToFind)
? acc.concat(value)
: (typeof value === 'object')
? acc.concat(findAllByKey(value, keyToFind))
: acc
, [])
}
// USAGE
findAllByKey(myObj, 'id')
You could make a recursive function like this:
idArray = []
function func(obj) {
idArray.push(obj.id)
if (!obj.children) {
return
}
obj.children.forEach(child => func(child))
}
Snippet for your sample:
const myObj = {
id: 1,
children: [{
id: 2,
children: [{
id: 3
}]
},
{
id: 4,
children: [{
id: 5,
children: [{
id: 6,
children: [{
id: 7,
}]
}]
}]
},
]
}
idArray = []
function func(obj) {
idArray.push(obj.id)
if (!obj.children) {
return
}
obj.children.forEach(child => func(child))
}
func(myObj)
console.log(idArray)
I found steve's answer to be most suited for my needs in extrapolating this out and creating a general recursive function. That said, I encountered issues when dealing with nulls and undefined values, so I extended the condition to accommodate for this. This approach uses:
Array.reduce() - It uses an accumulator function which appends the value's onto the result array. It also splits each object into it's key:value pair which allows you to take the following steps:
Have you've found the key? If so, add it to the array;
If not, have I found an object with values? If so, the key is possibly within there. Keep digging by calling the function on this object and append the result onto the result array; and
Finally, if this is not an object, return the result array unchanged.
Hope it helps!
const myObj = {
id: 1,
children: [{
id: 2,
children: [{
id: 3
}]
},
{
id: 4,
children: [{
id: 5,
children: [{
id: 6,
children: [{
id: 7,
}]
}]
}]
},
]
}
function findAllByKey(obj, keyToFind) {
return Object.entries(obj)
.reduce((acc, [key, value]) => (key === keyToFind)
? acc.concat(value)
: (typeof value === 'object' && value)
? acc.concat(findAllByKey(value, keyToFind))
: acc
, []) || [];
}
const ids = findAllByKey(myObj, 'id');
console.log(ids)
You can make a generic recursive function that works with any property and any object.
This uses Object.entries(), Object.keys(), Array.reduce(), Array.isArray(), Array.map() and Array.flat().
The stopping condition is when the object passed in is empty:
const myObj = {
id: 1,
anyProp: [{
id: 2,
thing: { a: 1, id: 10 },
children: [{ id: 3 }]
}, {
id: 4,
children: [{
id: 5,
children: [{
id: 6,
children: [{ id: 7 }]
}]
}]
}]
};
const getValues = prop => obj => {
if (!Object.keys(obj).length) { return []; }
return Object.entries(obj).reduce((acc, [key, val]) => {
if (key === prop) {
acc.push(val);
} else {
acc.push(Array.isArray(val) ? val.map(getIds).flat() : getIds(val));
}
return acc.flat();
}, []);
}
const getIds = getValues('id');
console.log(getIds(myObj));
Note: children is a consistent name, and id's wont exist outside
of a children object.
So from the obj, I would like to produce an array like this:
const idArray = [1, 2, 3, 4, 5, 6, 7]
Given that the question does not contain any restrictions on how the output is derived from the input and that the input is consistent, where the value of property "id" is a digit and id property is defined only within "children" property, save for case of the first "id" in the object, the input JavaScript plain object can be converted to a JSON string using JSON.stringify(), RegExp /"id":\d+/g matches the "id" property and one or more digit characters following the property name, which is then mapped to .match() the digit portion of the previous match using Regexp \d+ and convert the array value to a JavaScript number using addition operator +
const myObject = {"id":1,"children":[{"id":2,"children":[{"id":3}]},{"id":4,"children":[{"id":5,"children":[{"id":6,"children":[{"id":7}]}]}]}]};
let res = JSON.stringify(myObject).match(/"id":\d+/g).map(m => +m.match(/\d+/));
console.log(res);
JSON.stringify() replacer function can alternatively be used to .push() the value of every "id" property name within the object to an array
const myObject = {"id":1,"children":[{"id":2,"children":[{"id":3}]},{"id":4,"children":[{"id":5,"children":[{"id":6,"children":[{"id":7}]}]}]}]};
const getPropValues = (o, prop) =>
(res => (JSON.stringify(o, (key, value) =>
(key === prop && res.push(value), value)), res))([]);
let res = getPropValues(myObject, "id");
console.log(res);
Since the property values of the input to be matched are digits, all the JavaScript object can be converted to a string and RegExp \D can be used to replace all characters that are not digits, spread resulting string to array, and .map() digits to JavaScript numbers
let res = [...JSON.stringify(myObj).replace(/\D/g,"")].map(Number)
Using recursion.
const myObj = { id: 1, children: [ { id: 2, children: [ { id: 3 } ] }, { id: 4, children: [ { id: 5, children: [ { id: 6, children: [ { id: 7, } ] } ] } ] }, ]},
loop = (array, key, obj) => {
if (!obj.children) return;
obj.children.forEach(c => {
if (c[key]) array.push(c[key]); // is not present, skip!
loop(array, key, c);
});
},
arr = myObj["id"] ? [myObj["id"]] : [];
loop(arr, "id", myObj);
console.log(arr);
.as-console-wrapper { max-height: 100% !important; top: 0; }
You can make a recursive function with Object.entries like so:
const myObj = {
id: 1,
children: [{
id: 2,
children: [{
id: 3
}]
},
{
id: 4,
children: [{
id: 5,
children: [{
id: 6,
children: [{
id: 7,
}]
}]
}]
},
]
};
function findIds(obj) {
const entries = Object.entries(obj);
let result = entries.map(e => {
if (e[0] == "children") {
return e[1].map(child => findIds(child));
} else {
return e[1];
}
});
function flatten(arr, flat = []) {
for (let i = 0, length = arr.length; i < length; i++) {
const value = arr[i];
if (Array.isArray(value)) {
flatten(value, flat);
} else {
flat.push(value);
}
}
return flat;
}
return flatten(result);
}
var ids = findIds(myObj);
console.log(ids);
Flattening function from this answer
ES5 syntax:
var myObj = {
id: 1,
children: [{
id: 2,
children: [{
id: 3
}]
},
{
id: 4,
children: [{
id: 5,
children: [{
id: 6,
children: [{
id: 7,
}]
}]
}]
},
]
};
function findIds(obj) {
const entries = Object.entries(obj);
let result = entries.map(function(e) {
if (e[0] == "children") {
return e[1].map(function(child) {
return findIds(child)
});
} else {
return e[1];
}
});
function flatten(arr, flat = []) {
for (let i = 0, length = arr.length; i < length; i++) {
const value = arr[i];
if (Array.isArray(value)) {
flatten(value, flat);
} else {
flat.push(value);
}
}
return flat;
}
return flatten(result);
}
var ids = findIds(myObj);
console.log(ids);
let str = JSON.stringify(myObj);
let array = str.match(/\d+/g).map(v => v * 1);
console.log(array); // [1, 2, 3, 4, 5, 6, 7]
We use object-scan for a lot of our data processing needs now. It makes the code much more maintainable, but does take a moment to wrap your head around. Here is how you could use it to answer your question
// const objectScan = require('object-scan');
const find = (data, needle) => objectScan([needle], { rtn: 'value' })(data);
const myObj = { id: 1, children: [{ id: 2, children: [ { id: 3 } ] }, { id: 4, children: [ { id: 5, children: [ { id: 6, children: [ { id: 7 } ] } ] } ] }] };
console.log(find(myObj, '**.id'));
// => [ 7, 6, 5, 4, 3, 2, 1 ]
.as-console-wrapper {max-height: 100% !important; top: 0}
<script src="https://bundle.run/object-scan#13.7.1"></script>
Disclaimer: I'm the author of object-scan
import {flattenDeep} from 'lodash';
/**
* Extracts all values from an object (also nested objects)
* into a single array
*
* #param obj
* #returns
*
* #example
* const test = {
* alpha: 'foo',
* beta: {
* gamma: 'bar',
* lambda: 'baz'
* }
* }
*
* objectFlatten(test) // ['foo', 'bar', 'baz']
*/
export function objectFlatten(obj: {}) {
const result = [];
for (const prop in obj) {
const value = obj[prop];
if (typeof value === 'object') {
result.push(objectFlatten(value));
} else {
result.push(value);
}
}
return flattenDeep(result);
}
Below solution is generic which will return all values by matching nested keys as well e.g for below json object
{
"a":1,
"b":{
"a":{
"a":"red"
}
},
"c":{
"d":2
}
}
to find all values matching key "a" output should be return
[1,{a:"red"},"red"]
const findkey = (obj, key) => {
let arr = [];
if (isPrimitive(obj)) return obj;
for (let [k, val] of Object.entries(obj)) {
if (k === key) arr.push(val);
if (!isPrimitive(val)) arr = [...arr, ...findkey(val, key)];
}
return arr;
};
const isPrimitive = (val) => {
return val !== Object(val);
};
I need to be able to concatenate two JavaScript objects like the following:
let arr1 = [
{"0": { id: "abdc4051", date: "2017-01-24" }},
{"1": { id: "abdc4052", date: "2017-01-22" }}
];
let arr2 = [
{"0": { category: "Sport", data: {code: "abdc4051", name: "ab"} } },
{"1": { category: "Others", data: {code: "abdc4052", name: "abc"} } }
];
Does anyone have a script for this or know of a built in way to do this?
I want the date to be added in the data on arr2 with the condition code equal to id
Your object shape makes this harder than it should be. Are you certain you want the sequential properties in each object, or is that an artifact of logging/poor parsing?
You'll need to work around them if you actually need them, in the snippet below using Object.values() in creating a Map from arr1, and using Object.entries() in the final map() call on arr2 to store the sequential key and then reintroduce it in the return after the merge logic.
const
arr1 = [{ "0": { id: "abdc4051", date: "2017-01-24" } }, { "1": { id: "abdc4052", date: "2017-01-22" } }],
arr2 = [{ "0": { category: "Sport", data: { code: "abdc4051", name: "ab" } } }, { "1": { category: "Others", data: { code: "abdc4052", name: "abc" } } }],
// create map of dates: Map(2) { 'abdc4051' => '2017-01-24', 'abdc4052' => '2017-01-22' }
dateMap = new Map(arr1.map(o => {
const [{ id, date }] = Object.values(o);
return [id, date];
})),
// map over arr2, get date from Map and add it to 'data' if it exists
result = arr2.map(o => {
const [[k, _o]] = Object.entries(o);
const date = dateMap.get(_o.data.code);
return {
[k]: {
..._o,
data: { ..._o.data, ...(date ? { date } : {}) }
}
};
});
console.log(result);
.as-console-wrapper { max-height: 100% !important; top: 0; }
If you don't need the initial sequential keys the merge becomes much less verbose.
const
arr1 = [{ id: "abdc4051", date: "2017-01-24" }, { id: "abdc4052", date: "2017-01-22" }],
arr2 = [{ category: "Sport", data: { code: "abdc4051", name: "ab" } }, { category: "Others", data: { code: "abdc4052", name: "abc" } }],
dateMap = new Map(arr1.map(o => [o.id, o.date])),
result = arr2.map(o => (
{
...o,
data: { ...o.data, ...(dateMap.has(o.data.code) ? { date: dateMap.get(o.data.code) } : {}) }
}
));
console.log(result)
.as-console-wrapper { max-height: 100% !important; top: 0; }
I have an array
const a = [
{ name: "read-web-courses" },
{ name: "example" },
{ name: "t_gql" },
{ name: "ddddd" },
];
I am trying it to reduce it to the below given output , However I am stuck
Output
{0:"read-web-courses",1:"example",2:"t_gql",3:"ddddd"}
You could map the wanted property and assign the pairs to the object.
const
array = [{ name: "read-web-courses" }, { name: "example" }, { name: "t_gql" }, { name: "ddddd" }],
result = Object.assign({}, array.map(({ name }) => name));
console.log(result);
You can use Array.reduce like below.
const a = [
{ name: "read-web-courses" },
{ name: "example" },
{ name: "t_gql" },
{ name: "ddddd" },
];
const convert = arr => (
arr.reduce((total, value, index) => {
total[index] = value.name;
return total;
}, {})
)
console.log(convert(a));
This is accomplished using Array#reduce, where you can use the index from the reduce callback as the key of the new object:
const a = [ { name: "read-web-courses" }, { name: "example" }, { name: "t_gql" }, { name: "ddddd" }];
const res = a.reduce((r, o, i) => {
r[i] = o.name;
return r;
}, {});
console.log(res);
Also one more approach using Object#fromEntries and Array#map, where each object is converted to an array of key, value pairs:
const a = [ { name: "read-web-courses" }, { name: "example" }, { name: "t_gql" }, { name: "ddddd" }];
const res = Object.fromEntries(a.map((o, i) => [i, o.name]));
console.log(res)
I have an array of data which is a string of folders:
var data = [{ name: "/X" }, { name: "/X/Y" }, { name: "/X2" }, { name: "/X2/Z" }, { name: "/X/k" }]
For a component to display this items I need them sorted nested like these:
var data = [{ name: "/X", sub: [{ name: "/Y" }, { name: "/k" }]}, { name: "/X2" }, sub: [{ name: "/Z" }] }]
These items are just examples, the item count is 1000+ and the nested items can be unlimited too.
Any ideas how to do that?
You could do this with forEach and reduce methods and use one object to keep track of level based on the current part of the name property value.
const data = [{ name: "/X" }, { name: "/X/Y" }, { name: "/X2" }, { name: "/X2/Z" }, {name: '/X/K/1'}, {name: '/X/K/2'}]
const result = []
const level = {result}
data.forEach(({ name, ...rest }) => {
name.split('/').filter(Boolean).reduce((r, k) => {
if (!r[k]) {
r[k] = { result: [] }
r.result.push({
name: `/${k}`,
sub: r[k].result
})
}
return r[k]
}, level)
})
console.log(result)
Using reduce() and Map()
var data = [{ name: "/X" }, { name: "/X/Y" }, { name: "/X2" }, { name: "/X2/Z" }, { name: "/X/k" }]
var res = data.reduce((a, i) => {
let s = i.name.match(/\/\w+/g) || []
if (a.has(s[0])) {
let path = a.get(s[0])
i.name = s[1]
path.sub = path.sub || []
path.sub.push(i)
} else {
a.set(i.name, i)
}
return a
}, new Map())
console.log([...res.values()])
I would like to know how to change nested array object to object depending on key in javascript
I have objects obj1 and obj2, depending on key item type change the object.
function changeObj(obj){
let result = obj.reduce(function (acc, item) {
if(item.items.trim() !== "" && item.key.trim() !== ""){
acc[item.key] = item.items
return acc
}
return acc
}, {});
return result;
}
let result = this.changeObj(obj2)
var obj1 = [
{ id:0, items:["SG","AU"], count: 2, key:"countries"},
{ id:1, items:["finance"], count: 3 key:"info"}
]
var obj2 = [
{ id:0, items: "SG", key: "country"},
{ id:1, items: "details", key: "info"}
]
Expected Output:
// if items key is array
{
fields: {
countries: ["SG","AU",2],
info: ["finance",3]
}
}
//if items key is string
{
fields: {
country: "SG",
info: "details"
}
}
I think the reason your code is not running is because the wrong format of your objects (1 and 2). Your code is okay except the condition because trim() only works on string type so it errors on array. Try this code snippet
function changeObj(obj){
let result = obj.reduce(function (acc, item) {
acc[item.key] = item.items;
return acc;
}, {});
return result;
}
var obj1 = [
{ id:0, items:["SG","AU"], count: 2, key:"countries"},
{ id:1, items:["finance"], count: 3, key:"info"}
]
var obj2 = [
{ id:0, items: "SG", key: "country"},
{ id:1, items: "details", key: "info"}
]
console.log(changeObj(obj1));
const changeObj = obj =>
obj.reduce((acc, item) => {
if (Array.isArray(item.items)) {
acc[item.key] = [...item.items, item.count];
} else {
acc[item.key] = item.items;
}
return acc;
}, {});
var obj1 = [
{ id: 0, items: ['SG', 'AU'], count: 2, key: 'countries' },
{ id: 1, items: ['finance'], count: 3, key: 'info' }
];
var obj2 = [
{ id: 0, items: 'SG', key: 'country' },
{ id: 1, items: 'details', key: 'info' }
];
console.log(changeObj(obj1));
console.log(changeObj(obj2));
or cleaned up even more
const changeObj = obj =>
obj.reduce((acc, { items, key, count }) => {
Array.isArray(items) ? (acc[key] = [...items, count]) : (acc[key] = items);
return acc;
}, {});
var obj1 = [
{ id: 0, items: ['SG', 'AU'], count: 2, key: 'countries' },
{ id: 1, items: ['finance'], count: 3, key: 'info' }
];
var obj2 = [
{ id: 0, items: 'SG', key: 'country' },
{ id: 1, items: 'details', key: 'info' }
];
console.log(changeObj(obj1));
console.log(changeObj(obj2));