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I would like to get the keys of a JavaScript object as an array, either in jQuery or pure JavaScript.
Is there a less verbose way than this?
var foo = { 'alpha' : 'puffin', 'beta' : 'beagle' };
var keys = [];
for (var key in foo) {
keys.push(key);
}
Use Object.keys:
var foo = {
'alpha': 'puffin',
'beta': 'beagle'
};
var keys = Object.keys(foo);
console.log(keys) // ['alpha', 'beta']
// (or maybe some other order, keys are unordered).
This is an ES5 feature. This means it works in all modern browsers but will not work in legacy browsers.
The ES5-shim has a implementation of Object.keys you can steal
You can use jQuery's $.map.
var foo = { 'alpha' : 'puffin', 'beta' : 'beagle' },
keys = $.map(foo, function(v, i){
return i;
});
Of course, Object.keys() is the best way to get an Object's keys. If it's not available in your environment, it can be trivially shimmed using code such as in your example (except you'd need to take into account your loop will iterate over all properties up the prototype chain, unlike Object.keys()'s behaviour).
However, your example code...
var foo = { 'alpha' : 'puffin', 'beta' : 'beagle' };
var keys = [];
for (var key in foo) {
keys.push(key);
}
jsFiddle.
...could be modified. You can do the assignment right in the variable part.
var foo = { 'alpha' : 'puffin', 'beta' : 'beagle' };
var keys = [], i = 0;
for (keys[i++] in foo) {}
jsFiddle.
Of course, this behaviour is different to what Object.keys() actually does (jsFiddle). You could simply use the shim on the MDN documentation.
In case you're here looking for something to list the keys of an n-depth nested object as a flat array:
const getObjectKeys = (obj, prefix = '') => {
return Object.entries(obj).reduce((collector, [key, val]) => {
const newKeys = [ ...collector, prefix ? `${prefix}.${key}` : key ]
if (Object.prototype.toString.call(val) === '[object Object]') {
const newPrefix = prefix ? `${prefix}.${key}` : key
const otherKeys = getObjectKeys(val, newPrefix)
return [ ...newKeys, ...otherKeys ]
}
return newKeys
}, [])
}
console.log(getObjectKeys({a: 1, b: 2, c: { d: 3, e: { f: 4 }}}))
I don't know about less verbose but I was inspired to coerce the following onto one line by the one-liner request, don't know how Pythonic it is though ;)
var keys = (function(o){var ks=[]; for(var k in o) ks.push(k); return ks})(foo);
Summary
For getting all of the keys of an Object you can use Object.keys(). Object.keys() takes an object as an argument and returns an array of all the keys.
Example:
const object = {
a: 'string1',
b: 42,
c: 34
};
const keys = Object.keys(object)
console.log(keys);
console.log(keys.length) // we can easily access the total amount of properties the object has
In the above example we store an array of keys in the keys const. We then can easily access the amount of properties on the object by checking the length of the keys array.
Getting the values with: Object.values()
The complementary function of Object.keys() is Object.values(). This function takes an object as an argument and returns an array of values. For example:
const object = {
a: 'random',
b: 22,
c: true
};
console.log(Object.values(object));
Year 2022 and JavaScript still does not have a sound way to work with hashes?
This issues a warning but works:
Object.prototype.keys = function() { return Object.keys(this) }
console.log("Keys of an object: ", { a:1, b:2 }.keys() )
// Keys of an object: Array [ "a", "b" ]
// WARN: Line 8:1: Object prototype is read only, properties should not be added no-extend-native
That said, Extending Built-in Objects is Controversial.
If you decide to use Underscore.js you better do
var foo = { 'alpha' : 'puffin', 'beta' : 'beagle' };
var keys = [];
_.each( foo, function( val, key ) {
keys.push(key);
});
console.log(keys);
Here I want to read key name of obj.
Like "CIRTGroupBox1", "CIRTGroupBox2"
Try this :
var arr = [{
'CIRTGroupBox1': ''
}, {
'CIRTGroupBox2': ''
}, {
'CIRTGroupBox3': ''
}];
// Using array.map() method
var usingMapKeys = arr.map((obj) => Object.keys(obj)[0]);
// Using Object.entries() method
var usingEnteriesKeys = arr.map((obj) => Object.entries(obj)[0][0]);
console.log(usingMapKeys);
console.log(usingEnteriesKeys);
is it?
var x = {
"ob1": "value",
"ob2": {
"ob21": "value"
}
};
var keys = Object.keys(x);
console.log(keys);
You can do that using Object.keys method in JS like below
var keys = Object.keys(groupBoxesTemp);
This will return string array and each item in it is the key of this object.
If you want to read values pertaining those 2 keys, you can do like below using the for-in loop:
for(item in groupBoxesTemp){
console.log('key is: ', item);
console.log('value is: ', groupBoxesTemp[item]);
}
Based on your screenshot, temp is an array of objects which has 3 objects in it. You can do that too like below:
temp.forEach(function(item, index){
//key for all objects in the array will be logged.
console.log( Object.keys(item) );
});
I would like to get the keys of a JavaScript object as an array, either in jQuery or pure JavaScript.
Is there a less verbose way than this?
var foo = { 'alpha' : 'puffin', 'beta' : 'beagle' };
var keys = [];
for (var key in foo) {
keys.push(key);
}
Use Object.keys:
var foo = {
'alpha': 'puffin',
'beta': 'beagle'
};
var keys = Object.keys(foo);
console.log(keys) // ['alpha', 'beta']
// (or maybe some other order, keys are unordered).
This is an ES5 feature. This means it works in all modern browsers but will not work in legacy browsers.
The ES5-shim has a implementation of Object.keys you can steal
You can use jQuery's $.map.
var foo = { 'alpha' : 'puffin', 'beta' : 'beagle' },
keys = $.map(foo, function(v, i){
return i;
});
Of course, Object.keys() is the best way to get an Object's keys. If it's not available in your environment, it can be trivially shimmed using code such as in your example (except you'd need to take into account your loop will iterate over all properties up the prototype chain, unlike Object.keys()'s behaviour).
However, your example code...
var foo = { 'alpha' : 'puffin', 'beta' : 'beagle' };
var keys = [];
for (var key in foo) {
keys.push(key);
}
jsFiddle.
...could be modified. You can do the assignment right in the variable part.
var foo = { 'alpha' : 'puffin', 'beta' : 'beagle' };
var keys = [], i = 0;
for (keys[i++] in foo) {}
jsFiddle.
Of course, this behaviour is different to what Object.keys() actually does (jsFiddle). You could simply use the shim on the MDN documentation.
In case you're here looking for something to list the keys of an n-depth nested object as a flat array:
const getObjectKeys = (obj, prefix = '') => {
return Object.entries(obj).reduce((collector, [key, val]) => {
const newKeys = [ ...collector, prefix ? `${prefix}.${key}` : key ]
if (Object.prototype.toString.call(val) === '[object Object]') {
const newPrefix = prefix ? `${prefix}.${key}` : key
const otherKeys = getObjectKeys(val, newPrefix)
return [ ...newKeys, ...otherKeys ]
}
return newKeys
}, [])
}
console.log(getObjectKeys({a: 1, b: 2, c: { d: 3, e: { f: 4 }}}))
I don't know about less verbose but I was inspired to coerce the following onto one line by the one-liner request, don't know how Pythonic it is though ;)
var keys = (function(o){var ks=[]; for(var k in o) ks.push(k); return ks})(foo);
Summary
For getting all of the keys of an Object you can use Object.keys(). Object.keys() takes an object as an argument and returns an array of all the keys.
Example:
const object = {
a: 'string1',
b: 42,
c: 34
};
const keys = Object.keys(object)
console.log(keys);
console.log(keys.length) // we can easily access the total amount of properties the object has
In the above example we store an array of keys in the keys const. We then can easily access the amount of properties on the object by checking the length of the keys array.
Getting the values with: Object.values()
The complementary function of Object.keys() is Object.values(). This function takes an object as an argument and returns an array of values. For example:
const object = {
a: 'random',
b: 22,
c: true
};
console.log(Object.values(object));
Year 2022 and JavaScript still does not have a sound way to work with hashes?
This issues a warning but works:
Object.prototype.keys = function() { return Object.keys(this) }
console.log("Keys of an object: ", { a:1, b:2 }.keys() )
// Keys of an object: Array [ "a", "b" ]
// WARN: Line 8:1: Object prototype is read only, properties should not be added no-extend-native
That said, Extending Built-in Objects is Controversial.
If you decide to use Underscore.js you better do
var foo = { 'alpha' : 'puffin', 'beta' : 'beagle' };
var keys = [];
_.each( foo, function( val, key ) {
keys.push(key);
});
console.log(keys);
I would like to get the keys of a JavaScript object as an array, either in jQuery or pure JavaScript.
Is there a less verbose way than this?
var foo = { 'alpha' : 'puffin', 'beta' : 'beagle' };
var keys = [];
for (var key in foo) {
keys.push(key);
}
Use Object.keys:
var foo = {
'alpha': 'puffin',
'beta': 'beagle'
};
var keys = Object.keys(foo);
console.log(keys) // ['alpha', 'beta']
// (or maybe some other order, keys are unordered).
This is an ES5 feature. This means it works in all modern browsers but will not work in legacy browsers.
The ES5-shim has a implementation of Object.keys you can steal
You can use jQuery's $.map.
var foo = { 'alpha' : 'puffin', 'beta' : 'beagle' },
keys = $.map(foo, function(v, i){
return i;
});
Of course, Object.keys() is the best way to get an Object's keys. If it's not available in your environment, it can be trivially shimmed using code such as in your example (except you'd need to take into account your loop will iterate over all properties up the prototype chain, unlike Object.keys()'s behaviour).
However, your example code...
var foo = { 'alpha' : 'puffin', 'beta' : 'beagle' };
var keys = [];
for (var key in foo) {
keys.push(key);
}
jsFiddle.
...could be modified. You can do the assignment right in the variable part.
var foo = { 'alpha' : 'puffin', 'beta' : 'beagle' };
var keys = [], i = 0;
for (keys[i++] in foo) {}
jsFiddle.
Of course, this behaviour is different to what Object.keys() actually does (jsFiddle). You could simply use the shim on the MDN documentation.
In case you're here looking for something to list the keys of an n-depth nested object as a flat array:
const getObjectKeys = (obj, prefix = '') => {
return Object.entries(obj).reduce((collector, [key, val]) => {
const newKeys = [ ...collector, prefix ? `${prefix}.${key}` : key ]
if (Object.prototype.toString.call(val) === '[object Object]') {
const newPrefix = prefix ? `${prefix}.${key}` : key
const otherKeys = getObjectKeys(val, newPrefix)
return [ ...newKeys, ...otherKeys ]
}
return newKeys
}, [])
}
console.log(getObjectKeys({a: 1, b: 2, c: { d: 3, e: { f: 4 }}}))
I don't know about less verbose but I was inspired to coerce the following onto one line by the one-liner request, don't know how Pythonic it is though ;)
var keys = (function(o){var ks=[]; for(var k in o) ks.push(k); return ks})(foo);
Summary
For getting all of the keys of an Object you can use Object.keys(). Object.keys() takes an object as an argument and returns an array of all the keys.
Example:
const object = {
a: 'string1',
b: 42,
c: 34
};
const keys = Object.keys(object)
console.log(keys);
console.log(keys.length) // we can easily access the total amount of properties the object has
In the above example we store an array of keys in the keys const. We then can easily access the amount of properties on the object by checking the length of the keys array.
Getting the values with: Object.values()
The complementary function of Object.keys() is Object.values(). This function takes an object as an argument and returns an array of values. For example:
const object = {
a: 'random',
b: 22,
c: true
};
console.log(Object.values(object));
Year 2022 and JavaScript still does not have a sound way to work with hashes?
This issues a warning but works:
Object.prototype.keys = function() { return Object.keys(this) }
console.log("Keys of an object: ", { a:1, b:2 }.keys() )
// Keys of an object: Array [ "a", "b" ]
// WARN: Line 8:1: Object prototype is read only, properties should not be added no-extend-native
That said, Extending Built-in Objects is Controversial.
If you decide to use Underscore.js you better do
var foo = { 'alpha' : 'puffin', 'beta' : 'beagle' };
var keys = [];
_.each( foo, function( val, key ) {
keys.push(key);
});
console.log(keys);
Consider:
var object = {
foo: {},
bar: {},
baz: {}
}
How would I do this:
var first = object[0];
console.log(first);
Obviously, that doesn’t work because the first index is named foo,
not 0.
console.log(object['foo']);
works, but I don’t know it’s named foo. It could be named anything. I just want the first.
Just for fun this works in JS 1.8.5
var obj = {a: 1, b: 2, c: 3};
Object.keys(obj)[0]; // "a"
This matches the same order that you would see doing
for (o in obj) { ... }
If you want something concise try:
for (first in obj) break;
alert(first);
wrapped as a function:
function first(obj) {
for (var a in obj) return a;
}
they're not really ordered, but you can do:
var first;
for (var i in obj) {
if (obj.hasOwnProperty(i) && typeof(i) !== 'function') {
first = obj[i];
break;
}
}
the .hasOwnProperty() is important to ignore prototyped objects.
This will not give you the first one as javascript objects are unordered, however this is fine in some cases.
myObject[Object.keys(myObject)[0]]
If the order of the objects is significant, you should revise your JSON schema to store the objects in an array:
[
{"name":"foo", ...},
{"name":"bar", ...},
{"name":"baz", ...}
]
or maybe:
[
["foo", {}],
["bar", {}],
["baz", {}]
]
As Ben Alpert points out, properties of Javascript objects are unordered, and your code is broken if you expect them to enumerate in the same order that they are specified in the object literal—there is no "first" property.
for first key of object you can use
console.log(Object.keys(object)[0]);//print key's name
for value
console.log(object[Object.keys(object)[0]]);//print key's value
There is no way to get the first element, seeing as "hashes" (objects) in JavaScript have unordered properties. Your best bet is to store the keys in an array:
var keys = ["foo", "bar", "baz"];
Then use that to get the proper value:
object[keys[0]]
ES6
const [first] = Object.keys(obj)
Using underscore you can use _.pairs to get the first object entry as a key value pair as follows:
_.pairs(obj)[0]
Then the key would be available with a further [0] subscript, the value with [1]
I had the same problem yesterday. I solved it like this:
var obj = {
foo:{},
bar:{},
baz:{}
},
first = null,
key = null;
for (var key in obj) {
first = obj[key];
if(typeof(first) !== 'function') {
break;
}
}
// first is the first enumerated property, and key it's corresponding key.
Not the most elegant solution, and I am pretty sure that it may yield different results in different browsers (i.e. the specs says that enumeration is not required to enumerate the properties in the same order as they were defined). However, I only had a single property in my object so that was a non-issue. I just needed the first key.
You could do something like this:
var object = {
foo:{a:'first'},
bar:{},
baz:{}
}
function getAttributeByIndex(obj, index){
var i = 0;
for (var attr in obj){
if (index === i){
return obj[attr];
}
i++;
}
return null;
}
var first = getAttributeByIndex(object, 0); // returns the value of the
// first (0 index) attribute
// of the object ( {a:'first'} )
To get the first key of your object
const myObject = {
'foo1': { name: 'myNam1' },
'foo2': { name: 'myNam2' }
}
const result = Object.keys(myObject)[0];
// result will return 'foo1'
Based on CMS answer. I don't get the value directly, instead I take the key at its index and use this to get the value:
Object.keyAt = function(obj, index) {
var i = 0;
for (var key in obj) {
if ((index || 0) === i++) return key;
}
};
var obj = {
foo: '1st',
bar: '2nd',
baz: '3rd'
};
var key = Object.keyAt(obj, 1);
var val = obj[key];
console.log(key); // => 'bar'
console.log(val); // => '2nd'
My solution:
Object.prototype.__index = function(index)
{
var i = -1;
for (var key in this)
{
if (this.hasOwnProperty(key) && typeof(this[key])!=='function')
++i;
if (i >= index)
return this[key];
}
return null;
}
aObj = {'jack':3, 'peter':4, '5':'col', 'kk':function(){alert('hell');}, 'till':'ding'};
alert(aObj.__index(4));