Given a javascript object, how can I convert it to an array in ECMAScript-6 ?
For example, given:
var inputObj = {a:'foo', b:[1,2,3], c:null, z:55};
The expected output would be:
['foo', [1,2,3], null, 55]
The order of the elements in the result is not important to me.
Use (ES5) Array::map over the keys with an arrow function (for short syntax only, not functionality):
let arr = Object.keys(obj).map((k) => obj[k])
True ES6 style would be to write a generator, and convert that iterable into an array:
function* values(obj) {
for (let prop of Object.keys(obj)) // own properties, you might use
// for (let prop in obj)
yield obj[prop];
}
let arr = Array.from(values(obj));
Regrettably, no object iterator has made it into the ES6 natives.
map is known to be a bit slower than loops.
map that is the slow part, the slow part is probably the building of a throwaway array done by Object.keys. If you had a generator func that didn't use Object.keys then I'd expect it would be much closer in speed to for in.Reflect.enumerate(obj) that does exactly this. But I have no idea whether it would be faster, especially since it doesn't seem to be implemented anywhere yet. Btw, Object.keys is actually pretty fast in V8, sometimes faster than for in.just use Object.values
Object.values(inputObj); // => ['foo', [1,2,3], null, 55]
As a summary, in ES6, there are three (3) variations to convert an Object to an Array as follows:
const MyObjects = { key1: 'value 1', key2: 'value 2', };
// Method 1: Converts the keys to Array
// --------------------------------------
Object.keys(MyObjects);
// ['key1', 'key2']
// Method 2 Converts the Values to Array
// --------------------------------------
Object.values(MyObjects);
// ['value 1', 'value 2']
// Method 3 Converts both Values and Keys
// --------------------------------------
Object.entries(MyObjects);
// [ ['key1', 'value 1'], ['key2', 'value 2'] ]
Converting an Array back to an Object can be done as follows:
const array = [ ['one', 1], ['two', 2], ];
Object.fromEntries(array);
// { one: 1, two: 2 }
I like the old school way:
var i=0, arr=[];
for (var ob in inputObj)
arr[i++]=ob;
Old school wins the jsperf test by a large margin, if not the upvotes. Sometimes new additions are "mis-features."
obj, why is ob global?for (let ob i inputObj)
ob in for(var ob in inputObj) is supposed to be a property key. So inside the loop it should be arr[i++]=inputObj[ob];. This makes it 22% slower than the code you have now. But it's still much faster than the others in the linked jsperf.This can be achieved using the Array Comprehension syntax:
[for (key of Object.keys(inputObj)) inputObj[key]]
Usage example:
var inputObj = {a:'foo', b:[1,2,3], c:null, z:55};
var arr = [for (key of Object.keys(inputObj)) inputObj[key]];
console.log(arr);
// prints [ 'foo', [ 1, 2, 3 ], null, 55 ]
Object iterator - you are supposed to use Maps
ES7 way:
let obj = { a: "foo", b: "bar", c: 1, d: [1, 2, 3, 4] }
Object.values(obj)
// output --> ['foo', 'bar', 1, [1, 2, 3, 4]
The Object.values() method returns an array of a given object's own enumerable property values, in the same order as that provided by a for...in loop (the difference being that a for-in loop enumerates properties in the prototype chain as well).Array.map equivalent of @Bergi's arrow function (see MDN for more about Array.map).
Edit 2020: converted to snippet and added an alternative
const obj = {
a: 'foo',
b: [1, 2, 3],
c: null,
z: 55
},
nwArr = Object.keys(obj).map(k => obj[k]),
// Alternative
nwArr2 = Object.fromEntries(Object.entries(obj));
nwArr.a = "bar";
nwArr2.a = "foobar"
console.log(`obj.a: ${obj.a}, nwArr.a: ${nwArr.a}, nwArr2.a: ${nwArr2.a}`);
Object.keys(obj).map(k => obj[k])const address = {
street: "bew1111",
city: "err111",
country: "ind11"
};
const address2 = {
street: "bewscxsd",
city: "errdc",
country: "indcdsc"
};
we have two objects here and I am going to use 2 methods for assign both objects into Array
Object.entries()
Object.keys()
1st one starts here-----
var firstar = Object.entries(address);
here I assigned address into firstar and when you will run this you will get output like this
(3) [Array(2), Array(2), Array(2)]
2nd one starts here
var secstar = Object.keys(address2);
here I assigned address2 into secstar and when you will run this you will get output like this
(3) ["street", "city", "country"]
