Set seems like a nice way to create Arrays with guaranteed unique elements, but it does not expose any good way to get properties, except for generator [Set].values, which is called in an awkward way of mySet.values.next()
.
This would have been ok, if you could call map
and similar functions on Sets. But you cannot do that, as well.
I've tried Array.from
, but seems to be converting only array-like (NodeList and TypedArrays ?) objects to Array. Another try: Object.keys
does not work for Sets, and Set.prototype does not have similar static method.
So, the question: Is there any convenient inbuilt method for creating an Array with values of a given Set ? (Order of element does not really matter).
if no such option exists, then maybe there is a nice idiomatic one-liner for doing that ? like, using for...of
, or similar ?
if no such option exists, then maybe there is a nice idiomatic one-liner for doing that ? like, using for...of, or similar ?
Indeed, there are several ways to convert a Set to an Array:
Using Array.from:
Note: safer for TypeScript.
const array = Array.from(mySet);
Simply spreading the Set out in an array:
Note: Spreading a Set has issues when compiled with TypeScript (See issue #8856). It's safer to use Array.from
above instead.
const array = [...mySet];
The old-fashioned way, iterating and pushing to a new array (Sets do have forEach):
const array = [];
mySet.forEach(v => array.push(v));
Previously, using the non-standard, and now deprecated array comprehension syntax:
const array = [v for (v of mySet)];
via https://speakerdeck.com/anguscroll/es6-uncensored by Angus Croll
It turns out, we can use spread
operator:
var myArr = [...mySet];
Or, alternatively, use Array.from
:
var myArr = Array.from(mySet);
Array.from
and ...
Array.from
. developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…
chrome://flags/#enable-javascript-harmony
Remember it's experimental don't think for moment that this is a good solution for development.
Assuming you are just using Set
temporarily to get unique values in an array and then converting back to an Array, try using this:
_.uniq([])
This relies on using underscore or lo-dash.
Perhaps to late to the party, but you could just do the following:
const set = new Set(['a', 'b']);
const values = set.values();
const array = Array.from(values);
This should work without problems in browsers that have support for ES6 or if you have a shim that correctly polyfills the above functionality.
Edit: Today you can just use what @c69 suggests:
const set = new Set(['a', 'b']);
const array = [...set]; // or Array.from(set)
set.entries()
you will get array of pairs. You can use set.values()
to get the plain array.
var array = Array.from(set);
.entries
, nor .values
. As @Buffalo mentioned above - Array.from(set)
is enough.
Array.from()
did not work as expected. But now spread and Array.from()
both work just fine.
Use spread Operator to get your desired result
var arrayFromSet = [...set];
In my case the solution was:
var testSet = new Set();
var testArray = [];
testSet.add("1");
testSet.add("2");
testSet.add("2"); // duplicate item
testSet.add("3");
var someFunction = function (value1, value2, setItself) {
testArray.push(value1);
};
testSet.forEach(someFunction);
console.log("testArray: " + testArray);
Worked under IE11.
Using Set and converting it to an array is very similar to copying an Array...
So you can use the same methods for copying an array which is very easy in ES6
For example, you can use ...
Imagine you have this Set below:
const a = new Set(["Alireza", "Dezfoolian", "is", "a", "developer"]);
You can simply convert it using:
const b = [...a];
and the result is:
["Alireza", "Dezfoolian", "is", "a", "developer"]
An array and now you can use all methods that you can use for an array...
Other common ways of doing it:
const b = Array.from(a);
or using loops like:
const b = [];
a.forEach(v => b.push(v));
The code below creates a set from an array and then, using the ...
operator.
var arr=[1,2,3,4,5,6,7,8,9,1,2,3,4,5,6,7,8,9,];
var set=new Set(arr);
let setarr=[...set];
console.log(setarr);
SIMPLEST ANSWER
just spread the set inside []
let mySet = new Set()
mySet.add(1)
mySet.add(5)
mySet.add(5)
let arr = [...mySet ]
Result: [1,5]
Here is an easy way to get only unique raw values from array. If you convert the array to Set and after this, do the conversion from Set to array. This conversion works only for raw values, for objects in the array it is not valid. Try it by yourself.
let myObj1 = {
name: "Dany",
age: 35,
address: "str. My street N5"
}
let myObj2 = {
name: "Dany",
age: 35,
address: "str. My street N5"
}
var myArray = [55, 44, 65, myObj1, 44, myObj2, 15, 25, 65, 30];
console.log(myArray);
var mySet = new Set(myArray);
console.log(mySet);
console.log(mySet.size === myArray.length);// !! The size differs because Set has only unique items
let uniqueArray = [...mySet];
console.log(uniqueArray);
// Here you will see your new array have only unique elements with raw
// values. The objects are not filtered as unique values by Set.
// Try it by yourself.
I would prefer to start with removing duplications from an array and then try to sort. Return the 1st element from new array.
function processData(myArray) {
var s = new Set(myArray);
var arr = [...s];
return arr.sort((a,b) => b-a)[1];
}
console.log(processData([2,3,6,6,5]);
function countUniqueValues(arr) { return Array.from(new Set(arr)).length } console.log(countUniqueValues([1, 2, 3, 4, 4, 4, 7, 7, 12, 12, 13]))
Success story sharing
var array = [v for (v of mySet)];
does not work in chrome 46Array.from(mySet);
[...mySet]
has issues when compiled using Typescript (see this issue), so probably safer to useArray.from(mySet)
if you intend to convert to Typescript in the near future.