JavaScript Symbol Reference

Last Updated : 28 May, 2024

In JavaScript, the Symbol is a primitive data type introduced in ES6. It is created using the `Symbol()` function, which returns a unique symbol value each time it is called. Symbols are immutable and unique, making them useful for creating property keys that are guaranteed to be unique across different objects. They are often used to define non-enumerable object properties.

Syntax:

[Symbol.property](string)

Example: JavaScript code to show the working of this function.

JavaScript

// Creating some arrays
const Array1 = [1, 2, 3];
const Array2 = [4, 5, 6];

// Calling concat() function
let Array3 = Array1.concat(Array2);

// Printing the concatenated array
console.log(Array3);

// Calling Symbol.isConcatSpreadable symbol
Array2[Symbol.isConcatSpreadable] = false;
Array3 = Array1.concat(Array2);

// Printing the concatenated array
// after calling of Symbol.isConcatSpreadable symbol
console.log(Array3);

Output:

 Array [1, 2, 3, 4, 5, 6]
 Array [1, 2, 3, Array [4, 5, 6]]

The complete list of JavaScript Symbol is listed below:

JavaScript Symbol Constructor: In JavaScript, a constructor gets called when an object is created.

Constructor	Description	Example
Symbol()	Used to create a symbol object	Try

JavaScript Symbol Properties: A JavaScript property is a member of an object that associates a key with a value.

Static Property: A static property is a property that has the same value for the entire class.

Properties	Description	Example
asyncIterator	It sets an object as async iterable	Try
hasInstance	Determine if a given constructor object recognizes the object as its instance.	Try
isConcatSpreadable	Given object should be flattened to its array elements while using the Array.prototype.concat() method.	Try
iterator	It makes an element easier to use in for..of loop	Try
match	It identifies matching of a Regular Expression to a string	Try
matchAll	It returns Regular Expression that matches the String	Try
replace	Replace the matched substring of a string.	Try
search	Returns the index within a string that matches the regular expression.	Try
species	It is used to create a derived object from a function-valued property	Try
split	Specify the method that splits a string at the indices that match a regular expression.	Try
toStringTag	Creation of the default string description of an object.	Try
unscopables	Specify an object value of whose own and inherited property names are excluded from the environment bindings.	Try

Instance Properties: An instance property is a property that has a new copy for every new instance of the class.

Properties	Description	Example
constructor	Return the string constructor function for the object.	Try
description	Return the optional description of the specified symbol objects.	Try

JavaScript Symbol Methods: JavaScript methods are actions that can be performed on objects. There are two types of Symbol methods in JavaScript.

Static Method: If the method is called using the symbol class itself then it is called a static method.

Methods	Description	Example
for()	The Symbol.for() is used to search for the given symbol	Try
keyFor()	This key is retrieved from the global symbol registry.	Try

Instance Method: If the method is called on an instance of a Symbol then it is called an instance method.

Methods	Description	Example
toString()	convert the specified symbol object into the string.	Try
valueOf()	Return the primitive value of a given symbol object.	Try
@@toPrimitive()	Convert a given symbol object to a primitive value.	Try

JavaScript Symbol() Method

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