Reputation: 22440
How can I loop through all members in a JavaScript object, including values that are objects?
For example, how could I loop through this (accessing the "your_name" and "your_message" for each)?
var validation_messages = {
"key_1": {
"your_name": "jimmy",
"your_msg": "hello world"
},
"key_2": {
"your_name": "billy",
"your_msg": "foo equals bar"
}
}
Upvotes: 1836
Views: 2113572
Reputation:
I recently tackled a similar question a few days back. I encourage readers to check it out to gain an understanding of the concepts discussed in this answer. Additionally, I've utilized data from that question.
import { ArrayQueue } from "@ut8pia/classifier/queue/ArrayQueue.js";
import { Path } from "@ut8pia/fluent/util/Path.js";
import assert from "assert";
const root = {
name: 'root',
children: [
{name: 'Child 1',
children: [
{ name: 'Child 1.1', children: [] },
{ name: 'Child 1.2', children: [
{ name: 'Child 1.2.1', children: [] },
{ name: 'Child 1.2.2', children: [] },
{ name: 'Child 1.2.3', children: [] }
]}
]},
{name: 'Child 2', children: [
{ name: 'Child 2.1', children: [] },
{ name: 'Child 2.2', children: [] },
]},
{ name: 'Child 3', children: [] }
]},
n = 11;
This time, however, we'll generate paths of properties as entries [name, value]
instead of paths of objects in the tree. Since each object stores two inner properties
{name: ..., children: ...}
each object yields 3 properties: the outer property storing the object itself and the two inner ones. Consequently, we anticipate n * 3
properties, which also equals the expected count of property paths.
const
np = n * 3
Unlike before, where the children objects of each object within the tree were explicitly outlined by the children
property, this time, defining the children of each property in the tree requires explicit specification.
const children = ([name, obj]) => !(obj instanceof Object)? []
: typeof(obj) === 'function'? []
: Array.isArray(obj)? obj.map((item, i) => [i, item])
: Object.entries(obj);
Conceptually, however, the challenge of navigating through all the properties in the tree mirrors precisely the task of traversing all the objects within the tree. This correspondence becomes evident when examining the code.
const
space = path => path.across(children(path.last)),
search = new ArrayQueue()
.let(Path.of([undefined, root]))
.search(space)
You can validate the proposed solution by:
const
assert.equal(search.toArray().length, np)
Upvotes: 0
Reputation: 3358
var validation_messages = {
"key_1": {
"your_name": "jimmy",
"your_msg": "hello world"
},
"key_2": {
"your_name": "billy",
"your_msg": "foo equals bar"
}
}
for ( const item in validation_messages ) {
console.log( item )
console.log( validation_messages[item]["your_name"] )
console.log( validation_messages[item]["your_msg"] )
console.log( '---')
}
Upvotes: 0
Reputation: 11069
This walks through your multidimensional object composed of sub-objects, arrays and string and apply a custom function:
export const iterate = (object, func) => {
const entries = Object.entries(object).map(([key, value]) =>
Array.isArray(value)
? [key, value.map(e => iterate(e, func))]
: typeof value === 'object'
? [key, iterate(value, func)]
: [key, func(value)]
);
return Object.fromEntries(entries);
};
Usage:
const r = iterate(data, e=>'converted_'+e);
console.log(r);
Upvotes: 2
Reputation: 2605
There are so many ways to traverse an object. Please have a look at below examples.
var obj = {'name':'John Doe','email':'johndoe@example.com'}
Approach 1
var keys = Object.keys(obj)
for(var i= 0; i < keys.length;i++){
console.log(keys[i]+ ': ' + obj[keys[i]])
}
Approach 2
for(var key in obj){
console.log(key+': '+ obj[key])
}
Approach 3
Object.keys(obj).forEach(function (key) {
console.log(key+ ': ' + obj[key])
})
Upvotes: 13
Reputation: 27491
using lodash _.forEach:
_.forEach({ 'a': 1, 'b': 2 }, function(value, key) {
console.log(key, value);
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.21/lodash.min.js"></script>
Upvotes: 3
Reputation: 138
var validation_messages = {
"key_1": {
"your_name": "jimmy",
"your_msg": "hello world"
},
"key_2": {
"your_name": "billy",
"your_msg": "foo equals bar"
}
}
for (var i in validation_messages) {
console.log("i = \"" + i + "\"");
console.log("validation_messages[\"" + i + "\"] = ");
console.log(validation_messages[i]);
console.log("\n");
for (var j in validation_messages[i]) {
console.log("j = \"" + j + "\"");
console.log("validation_messages[\"" + i + "\"][\"" + j + "\"] = \"" + validation_messages[i][j] + "\"");
console.log("\n");
}
console.log('\n');
}
Outputs:
i = "key_1"
validation_messages["key_1"] =
{
your_name:"jimmy",
your_msg:"hello world"
}
j = "your_name"
validation_messages["key_1"]["your_name"] = "jimmy"
j = "your_msg"
validation_messages["key_1"]["your_msg"] = "hello world"
i = "key_2"
validation_messages["key_2"] =
{
your_name:"billy",
your_msg:"foo equals bar"
}
j = "your_name"
validation_messages["key_2"]["your_name"] = "billy"
j = "your_msg"
validation_messages["key_2"]["your_msg"] = "foo equals bar"
Upvotes: 4
Reputation: 56497
(Found here):
var lunch = {
sandwich: 'ham',
age: 48,
};
lunch.forEach2(function (item, key) {
console.log(key);
console.log(item);
});
Code:
if (!Object.prototype.forEach2) {
Object.defineProperty(Object.prototype, 'forEach2', {
value: function (callback, thisArg) {
if (this == null) {
throw new TypeError('Not an object');
}
thisArg = thisArg || window;
for (var key in this) {
if (this.hasOwnProperty(key)) {
callback.call(thisArg, this[key], key, this);
}
}
}
});
}
Upvotes: 1
Reputation: 92587
JSON.stringify(validation_messages,(field,value)=>{
if(!field) return value;
// ... your code
return value;
})
In this solution we use replacer which allows to deep traverse the whole object and nested objects - on each level you will get all fields and values. If you need to get the full path to each field, look here.
var validation_messages = {
"key_1": {
"your_name": "jimmy",
"your_msg": "hello world"
},
"key_2": {
"your_name": "billy",
"your_msg": "foo equals bar",
"deep": {
"color": "red",
"size": "10px"
}
}
}
JSON.stringify(validation_messages,(field,value)=>{
if(!field) return value;
console.log(`key: ${field.padEnd(11)} - value: ${value}`);
return value;
})
Upvotes: 0
Reputation: 104850
A few ways to do that...
1) A two-layer for...in loop...
for (let key in validation_messages) {
const vmKeys = validation_messages[key];
for (let vmKey in vmKeys) {
console.log(vmKey + vmKeys[vmKey]);
}
}
2) Using Object.key
Object.keys(validation_messages).forEach(key => {
const vmKeys = validation_messages[key];
Object.keys(vmKeys).forEach(key => {
console.log(vmKeys + vmKeys[key]);
});
});
3) Recursive function
const recursiveObj = obj => {
for(let key in obj){
if(!obj.hasOwnProperty(key)) continue;
if(typeof obj[key] !== 'object'){
console.log(key + obj[key]);
} else {
recursiveObj(obj[key]);
}
}
}
And call it like:
recursiveObj(validation_messages);
Upvotes: 9
Reputation: 111
var obj = {
name: "SanD",
age: "27"
}
Object.keys(obj).forEach((key) => console.log(key,obj[key]));
To loop through the JavaScript Object we can use forEach and to optimize the code we can use the arrow function.
Upvotes: 3
Reputation: 1785
The solution that works for me is the following:
_private.convertParams = function(params){
var params = [];
Object.keys(values).forEach(function(key) {
params.push({"id":key, "option":"Igual", "value":params[key].id})
});
return params;
}
Upvotes: 0
Reputation: 13298
This answer is an aggregate of the solutions that were provided in this post with some performance feedbacks. I think there is two use cases and the OP didn't mention if he needs to access the keys in order use them during the loop process.
✔ The of
and Object.keys
approach
let k;
for (k of Object.keys(obj)) {
/* k : key
* obj[k] : value
*/
}
✔ The in
approach
let k;
for (k in obj) {
/* k : key
* obj[k] : value
*/
}
Use this one with caution, as it could print prototype'd properties of obj
✔ The ES7 approach
for (const [key, value] of Object.entries(obj)) {
}
However, at the time of the edit I wouldn't recommend the ES7 method, because JavaScript initializes a lot of variables internally to build this procedure (see the feedbacks for proof). Unless you are not developing a huge application which deserves optimization, then it is OK, but if optimization is your priority, you should think about it.
✔ The of
and Object.values
approach
let v;
for (v of Object.values(obj)) {
}
Object.keys
or Object.values
performance is negligibleFor instance,
const keys = Object.keys(obj);
let i;
for (i of keys) {
//
}
// same as
for (i of Object.keys(obj)) {
//
}
For Object.values
case, using a native for
loop with cached variables in Firefox seems to be a little faster than using a for...of
loop. However, the difference is not that important and Chrome is running for...of
faster than native for
loop, so I would recommend to use for...of
when dealing with Object.values
in any cases (4th and 6th tests).
In Firefox, the for...in
loop is really slow, so when we want to cache the key during the iteration it is better to use Object.keys
. Plus Chrome is running both structure at equal speed (first and last tests).
You can check the tests here: https://jsperf.com/es7-and-misc-loops
Upvotes: 68
Reputation: 9279
ECMAScript 2017, just finalized a month ago, introduces Object.values(). So now you can do this:
let v;
for (v of Object.values(validation_messages))
console.log(v.your_name); // jimmy billy
Upvotes: 5
Reputation: 53933
In ES6/2015 you can loop through an object like this (using the arrow function):
Object.keys(myObj).forEach(key => {
console.log(key); // the name of the current key.
console.log(myObj[key]); // the value of the current key.
});
In ES7/2016 you can use Object.entries
instead of Object.keys
and loop through an object like this:
Object.entries(myObj).forEach(([key, val]) => {
console.log(key); // the name of the current key.
console.log(val); // the value of the current key.
});
The above would also work as a one-liner:
Object.entries(myObj).forEach(([key, val]) => console.log(key, val));
In case you want to loop through nested objects as well, you can use a recursive function (ES6):
const loopNestedObj = obj => {
Object.keys(obj).forEach(key => {
if (obj[key] && typeof obj[key] === "object") loopNestedObj(obj[key]); // recurse.
else console.log(key, obj[key]); // or do something with key and val.
});
};
The same as function above, but with ES7 Object.entries()
instead of Object.keys()
:
const loopNestedObj = obj => {
Object.entries(obj).forEach(([key, val]) => {
if (val && typeof val === "object") loopNestedObj(val); // recurse.
else console.log(key, val); // or do something with key and val.
});
};
Here we loop through nested objects change values and return a new object in one go using Object.entries()
combined with Object.fromEntries()
(ES10/2019):
const loopNestedObj = obj =>
Object.fromEntries(
Object.entries(obj).map(([key, val]) => {
if (val && typeof val === "object") [key, loopNestedObj(val)]; // recurse
else [key, updateMyVal(val)]; // or do something with key and val.
})
);
Another way of looping through objects is by using for ... in and for ... of. See vdegenne's nicely written answer.
Upvotes: 459
Reputation: 1
In my case (on the basis of the preceding) it is possible for any number of levels.
var myObj = {
rrr: undefined,
pageURL : "BLAH",
emailBox : {model:"emailAddress", selector:"#emailAddress"},
passwordBox: {model:"password" , selector:"#password"},
proba: {odin:{dva:"rr",trr:"tyuuu"}, od:{ff:5,ppa:{ooo:{lll:'lll'}},tyt:'12345'}}
};
function lookdeep(obj,p_Name,gg){
var A=[], tem, wrem=[], dd=gg?wrem:A;
for(var p in obj){
var y1=gg?'':p_Name, y1=y1 + '.' + p;
if(obj.hasOwnProperty(p)){
var tem=obj[p];
if(tem && typeof tem=='object'){
a1=arguments.callee(tem,p_Name,true);
if(a1 && typeof a1=='object'){for(i in a1){dd.push(y1 + a1[i])};}
}
else{
dd.push(y1 + ':' + String(tem));
}
}
};
return dd
};
var s=lookdeep(myObj,'myObj',false);
for (var x=0; x < s.length; ++x) {
console.log(s[x]+'\n');}
Result:
["myObj.rrr:undefined",
"myObj.pageURL:BLAH",
"myObj.emailBox.model:emailAddress",
"myObj.emailBox.selector:#emailAddress",
"myObj.passwordBox.model:password",
"myObj.passwordBox.selector:#password",
"myObj.proba.odin.dva:rr",
"myObj.proba.odin.trr:tyuuu",
"myObj.proba.od.ff:5",
"myObj.proba.od.ppa.ooo.lll:lll",
"myObj.proba.od.tyt:12345"]
Upvotes: -7
Reputation: 99
I couldn't get the previous answere to do quite what I was after.
After playing around with the other replies here, I made this. It's hacky, but it works!
For this object:
var myObj = {
pageURL : "BLAH",
emailBox : {model:"emailAddress", selector:"#emailAddress"},
passwordBox: {model:"password" , selector:"#password"}
};
... this code:
// Get every value in the object into a separate array item ...
function buildArray(p_MainObj, p_Name) {
var variableList = [];
var thisVar = "";
var thisYes = false;
for (var key in p_MainObj) {
thisVar = p_Name + "." + key;
thisYes = false;
if (p_MainObj.hasOwnProperty(key)) {
var obj = p_MainObj[key];
for (var prop in obj) {
var myregex = /^[0-9]*$/;
if (myregex.exec(prop) != prop) {
thisYes = true;
variableList.push({item:thisVar + "." + prop,value:obj[prop]});
}
}
if ( ! thisYes )
variableList.push({item:thisVar,value:obj});
}
}
return variableList;
}
// Get the object items into a simple array ...
var objectItems = buildArray(myObj, "myObj");
// Now use them / test them etc... as you need to!
for (var x=0; x < objectItems.length; ++x) {
console.log(objectItems[x].item + " = " + objectItems[x].value);
}
... produces this in the console:
myObj.pageURL = BLAH
myObj.emailBox.model = emailAddress
myObj.emailBox.selector = #emailAddress
myObj.passwordBox.model = password
myObj.passwordBox.selector = #password
Upvotes: 3
Reputation: 4728
An optimized and improved version of AgileJon's answer:
var key, obj, prop, owns = Object.prototype.hasOwnProperty;
for (key in validation_messages ) {
if (owns.call(validation_messages, key)) {
obj = validation_messages[key];
for (prop in obj ) {
// Using obj.hasOwnProperty might cause you headache if there is
// obj.hasOwnProperty = function(){return false;}
// but 'owns' will always work
if (owns.call(obj, prop)) {
console.log(prop, "=", obj[prop]);
}
}
}
}
Upvotes: 33
Reputation: 2603
I think it's worth pointing out that jQuery sorts this out nicely with $.each()
.
See: .each()
Example:
$('.foo').each(function() {
console.log($(this));
});
$(this)
being the single item inside the object. Swap $('.foo')
to a variable if you don't want to use jQuery's selector engine.
Upvotes: 3
Reputation: 349
Using ES8 Object.entries() should be a more compact way to achieve this.
Object.entries(validation_messages).map(([key,object]) => {
alert(`Looping through key : ${key}`);
Object.entries(object).map(([token, value]) => {
alert(`${token} : ${value}`);
});
});
Upvotes: 0
Reputation: 53626
for (var key in validation_messages) {
// skip loop if the property is from prototype
if (!validation_messages.hasOwnProperty(key)) continue;
var obj = validation_messages[key];
for (var prop in obj) {
// skip loop if the property is from prototype
if (!obj.hasOwnProperty(prop)) continue;
// your code
alert(prop + " = " + obj[prop]);
}
}
Upvotes: 2263
Reputation: 1070
p is the value
for (var key in p) {
alert(key + ' => ' + p[key]);
}
OR
Object.keys(p).forEach(key => { console.log(key, p[key]) })
Upvotes: 15
Reputation: 25751
Under ECMAScript 5, you can combine Object.keys()
and Array.prototype.forEach()
:
var obj = {
first: "John",
last: "Doe"
};
//
// Visit non-inherited enumerable keys
//
Object.keys(obj).forEach(function(key) {
console.log(key, obj[key]);
});
Upvotes: 922
Reputation: 1572
In ES7 you can do:
for (const [key, value] of Object.entries(obj)) {
//
}
Upvotes: 12
Reputation: 6086
Another option:
var testObj = {test: true, test1: false};
for(let x of Object.keys(testObj)){
console.log(x);
}
Upvotes: 6
Reputation: 28131
Using Underscore.js’s _.each
:
_.each(validation_messages, function(value, key){
_.each(value, function(value, key){
console.log(value);
});
});
Upvotes: 101
Reputation: 1269
Here comes the improved and recursive version of AgileJon's solution (demo):
function loopThrough(obj){
for(var key in obj){
// skip loop if the property is from prototype
if(!obj.hasOwnProperty(key)) continue;
if(typeof obj[key] !== 'object'){
//your code
console.log(key+" = "+obj[key]);
} else {
loopThrough(obj[key]);
}
}
}
loopThrough(validation_messages);
This solution works for all kinds of different depths.
Upvotes: 5
Reputation: 104820
If you use recursion you can return object properties of any depth-
function lookdeep(object){
var collection= [], index= 0, next, item;
for(item in object){
if(object.hasOwnProperty(item)){
next= object[item];
if(typeof next== 'object' && next!= null){
collection[index++]= item +
':{ '+ lookdeep(next).join(', ')+'}';
}
else collection[index++]= [item+':'+String(next)];
}
}
return collection;
}
//example
var O={
a:1, b:2, c:{
c1:3, c2:4, c3:{
t:true, f:false
}
},
d:11
};
var lookdeepSample= 'O={'+ lookdeep(O).join(',\n')+'}';
/* returned value: (String)
O={
a:1,
b:2,
c:{
c1:3, c2:4, c3:{
t:true, f:false
}
},
d:11
}
*/
Upvotes: 60
Reputation: 6782
The problem with this
for (var key in validation_messages) {
var obj = validation_messages[key];
for (var prop in obj) {
alert(prop + " = " + obj[prop]);
}
}
is that you’ll also loop through the primitive object's prototype.
With this one you will avoid it:
for (var key in validation_messages) {
if (validation_messages.hasOwnProperty(key)) {
var obj = validation_messages[key];
for (var prop in obj) {
if (obj.hasOwnProperty(prop)) {
alert(prop + " = " + obj[prop]);
}
}
}
}
Upvotes: 397
Reputation: 9681
for(var key in validation_messages){
for(var subkey in validation_messages[key]){
//code here
//subkey being value, key being 'yourname' / 'yourmsg'
}
}
Upvotes: 9
Reputation: 124335
for(var k in validation_messages) {
var o = validation_messages[k];
do_something_with(o.your_name);
do_something_else_with(o.your_msg);
}
Upvotes: 34