JavaScript syntax: Difference between revisions

Revision as of 00:46, 16 January 2021

Revision as of 21:30, 22 January 2021

Line 410:

<syntaxhighlight lang="javascript">

var x = Symbol(1);

var y = Symbol(1);

x === y; // => false

arr=[x,y];

var symbolObject = {};

arr[x]=1;

var normalObject = {};

arr[y]=2; // x and y are unique keys for the array arr

arr[x]; // displays 1

// since x and y are unique,

arr[y]; // displays 2

// they can be used as unique keys in an object

x=Symbol(3);

symbolObject[x] = 1;

arr; // displays [Symbol(1),Symbol(1)]

symbolObject[y] = 2;

arr[x]; // is now undefined

x=Symbol(1);

arrsymbolObject[x]; // undefined=> 1

symbolObject[y]; // => 2

// as compared to normal numeric keys

normalObject[1] = 1;

normalObject[1] = 2; // overrides the value of 1

normalObject[1]; // => 2

// changing the value of x does not change the key stored in the object

x = Symbol(3);

arrsymbolObject[x]; // is now=> undefined

// changing x back just creates another unique Symbol

x = Symbol(1);

symbolObject[x]; // => undefined

</syntaxhighlight>

The<!-- Symbolwhat wrapperdoes alsothis providesmean accessand tohow ais it "variable free iterator."?

"The Symbol wrapper also provides access to a [sic] variable free iterator."

<syntaxhighlight lang="javascript">

Line 432 ⟶ 449:

while ((exv=ex.next().value)!=undefined) console.log(exv); // displays 1,2,3,4

</syntaxhighlight>

-->

==Native objects==