Develop Reference

Set and spread operator [duplicate]

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);

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)

Use spread Operator to get your desired result
var arrayFromSet = [...set];

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]

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);
value1 equals value2 => The value contained in the the current position in the Set. The same value is passed for both arguments
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 simplistic way to doing this
const array = [...new Set([1,1,2,3,3,4,5])]
console.log(array)

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]))

Learning to programming JavaScript, but I'm stuck

Yesterday I started learning JavaScript. I am using the system Codecademy, but I'm stuck. When I say "stuck", I mean I have assignment with which I cannot see what is wrong.
The assignment is:
Create an array, myArray. Its first element should be a number, its second should be a boolean, its third should be a string, and its fourth should be...an object! You can add as many elements of any type as you like after these first four.
This is the code I made:
var myObj = {
name: 'Hansen'
};
var myArray = [12,true, "Steen" ,myObj.name];
The error:
Oops, try again.
Is the fourth element of myArray an object?
Hope you can help me.

The problem with your fourth element is you are passing a string because myObj.name is defined as Hansen. Pass the object instead:
var myArray = [12,true, "Steen" ,myObj];

I don't know that site, but you can do:
var myArray = [
12,
true,
"Steen",
{name: 'Hansen'}
];
What you are passing to the array is the value of the name property of your object instead of the object itself.

Your passing in the name property instead of the object for the fourth array parameter as you probably already know from the other anwers.
As your learning here are a few ways to do exactly the same thing as your accomplishing here.
Your way corrected:
var myObj = {
name: 'Hansen'
};
var myArray = [12, true, "Steen", myObj];
Other ways:
// Method 1
var myArray = [12, true, "Steen", {name: 'Hansen'}];
// Method 2
var myObj = new Object();
myObj.name = "Hansen";
var myArray = new Array(12, true, "Steen", myObj);
// Method 3
var myObj = {};
myObj['name'] = 'Hansen'
var myArray = [
12, true, 'Steen', myObj
]
Each method shows a few different ways to do the same thing, you can mix and match the equivalent parts of code to get the same job done. It's basically inter changing between the normal JavaScript syntax and object literal syntax.

Javascript defining array. "arrayception"

I am trying to create a list of "items" in a canvas game. For example, an array named list. Each element must contain the information about each item. First element will contain something different. I will remove first one with 'shift()' command. Like :
list.shift();
list[0]['name']
list[0]['id']
list[0]['x']
list[0]['y']
list[1]['name']
list[1]['id']
list[1]['x']
list[1]['y']
but i don't know how to define something like this. normally i define arrays like
{"name" : xx, "id" : 5 ... }
but this works like :
list['name']
list['id']

use:
var list = [];
list[0] = {name: 'xx', id: 0, /*etc*/};
list[1] = {name: 'yy', id: 1, /*etc*/};
it creates an array of objects. You can use it like this:
var first = list.shift();
first.name; //=> xx
//or
var first = list[0];
first.name; //=> xx
Note: using {...} (Object literal) creates an Object, not an Array. An array can be created using an Array literal: [...]. Although an object is sometimes said to be an Associative Array, it is not an Array object, so things like {...}.shift() will not work for Objects.

There are no associative arrays in javascript.
so for instance , when you do
var _array = []
_array["field1"] ="value";
you are actually adding a property to the _array object .
_array.field1 = value <=> _array["field1"] ="value";
so if you want to create a collection of objects , do
var collection =[];
var myObject = {"field1":"value1"};
collection.push(myObject);

How can I add an array to an array of arrays using jQuery?

I have an array, as below:
var cString = [
['1','Techdirt','www.techdirt.com'],
['2','Slashdot','slashdot.org'],
['3','Wired','wired.com']
];
to this array I want to add another in the same format:
var test = ['4','Stackoverflow','stackoverflow.com']
I've tried using:
var newArray = $.merge(cString, test);
But console.log(newArray); outputs:
[►Array,►Array,►Array,'4','Stackoverflow','stackoverflow.com']
So I'm assuming that I'm missing something obvious. Or attempting something stupid...help?

jQuery is not needed for this. Just use the Array's .push() method to add it to the main array.
var test = ['4','Stackoverflow','stackoverflow.com']
cString.push( test );
What $.merge() does is it walks through the second array you pass it and copies its items one by one into the first.
EDIT:
If you didn't want to modify the original array, you could make a copy of it first, and .push() the new Array into the copy.
var cString = [
['1','Techdirt','www.techdirt.com'],
['2','Slashdot','slashdot.org'],
['3','Wired','wired.com']
];
var test = ['4','Stackoverflow','stackoverflow.com']
var newArray = cString.slice();
newArray.push( test );

In addition to push as described by patrick, if you want to create a new list rather than changing the old, you can add arrays together with Array#concat:
var newArray= cString.concat([['4','Stackoverflow','stackoverflow.com']]);

you can use merge function like this
var newArray = $.merge($.merge([], cString), test);

Javascript, jquery - Call array position by using a variable name

I have 2 arrays:
var array1 = [50,60];
var array2 = [120,180];
I am passing a value to a variable like this:
var curId = $(this).attr('id');
I want to set the content of #result to a computation like this:
$(#result).text(number * curId[0]);
Number is a variable predefined by me, and curId[0] shoul actually translate to array1[0] or array2[0], depending on the css class.
Can anyone tell me the right syntax for this? I'm pretty noob at js.
Thanks.

You can use a variable to hold the array that you want to use:
var myArray;
if (something)
myArray = array1;
else
myArray = array2;
$('#result').text(number * myArray[0]);
If you're trying to get the array in a variable from a string containing the name of the variable, you should use an object, like this:
var arrays = {
array1: [50,60],
array2: [120,180]
};
var myArray = arrays[curId];
$('#result').text(number * myArray[0]);

So curId will be the string "array1" or "array2"? Then you'd do it like this:
var lookups = {
array1: [50, 60],
array2: [120,180]
};
var curId = $(this).attr('id');
$('#result').text(number * lookups[curId[0]]);
What that does is create an object (lookups) to contain this information you're looking up. That object has the properties array1 and array1, which are your arrays. You get the string "array1" or "array2" from the ID of your element into the variable curId, and then you use the fact that Javascript lets you look up properties by their name using [] syntax. All of these are the same:
a = lookups.array1;
// is the same as
a = lookups["array1"];
// is the same as
a = lookups["array" + "1"];
// is the same as
s = "array1";
a = lookups[s];
Technically, if your arrays are declared at global scope, you could do that without using the lookups object, but if you're fairly new to Javascript I won't go into why, and regardless, I'd recommend using one.