JavaScript Map Methods

Create Map Methods In JavaScript

A Map holds key-value pairs and the keys can be of any data type.

The map maintains the insertion order of keys and provides a size property. Common methods for working with maps include set(), get(), delete() and clear().

Map Methods can be iterated directly and have built-in methods for managing key-value pairs. Map Methods unlike JavaScript Objects, do not have default keys.

Common Syntax Of Map Methods In JavaScript

Glossary:

Iterable

Object values can be looped in a “for of” loop.

Default

Define default values in none provided.

Declaration

Used to define variables, functions, and constants.

Method

Function defined within a object.

Constructor

Special method within a class used to initialize and create objects of that class.

Common Methods For Map Methods

Ojamboshop.com Learning JavaScript Map Methods

Name	Description	Example
Map()	Create a new Map.	new Map();
set()	Add elements to a Map.	set(“age”, 24);
get()	Get value of a key in a Map.	get(“age”);
size	Return number of elements in a map.	prices.size;
delete()	Removes an element in a map.	prices.delete(“Bread”);
has()	Returns true if specified key exists in a map.	prices.has(‘Bread’);
clear()	Removes all elements in a map.	prices.clear();
Name	Description	Example

JavaScript Map Methods Snippet

// OjamboShop.com Learning JavaScript Map Methods Tutorial

// Create Map Via Passing Array
let prices = new Map([
	["Milk", 10],
	["Butter", 5],
	["Bread", 2],
]);
console.log(typeof prices);
console.log(JSON.stringify(Object.fromEntries(prices)));

// Create Map Elements Via Set
let costs = new Map();
costs.set("Juice", 3);
costs.set("Cereal", 4);
costs.set("Soap", 6);
console.log(typeof costs);
console.log(JSON.stringify(Object.fromEntries(costs)));

// Retrieve Values
console.log("Milk price: " + prices.get("Milk"));
console.log("Butter price: " + prices.get("Butter"));
console.log("Bread price: " + prices.get("Bread"));
console.log("Juice cost " + costs.get("Juice"));
console.log("Cereal cost " + costs.get("Cereal"));
console.log("Soap cost " + costs.get("Soap"));

// List All Elements In Map
prices.forEach (function(value, key) {
	console.log(`${key} price: ${value}`);
});
costs.forEach (function(value, key) {
	console.log(`${key} cost: ${value}`);
});

// Number Of Elements
console.log("The number of elements for prices is " + prices.size);
console.log("The number of elements for costs is " + costs.size);

// Boolean Check
console.log("Milk check is " + prices.has("Milk"));
console.log("Juice check is " + costs.has("Juice"));

// Remove Some Elements
prices.delete("Milk");
costs.delete("Juice");
console.log("Milk check is " + prices.has("Milk"));
console.log("Juice check is " + costs.has("Juice"));

// Remove All Elements
prices.clear();
costs.clear();
console.log("The number of elements for prices is " + prices.size);
console.log("The number of elements for costs is " + costs.size);

Usage

You can use any IDE or text editor and the web browser to compile and execute JavaScript code. For this tutorial, the OjamboShop.com Learning JavaScript Course Web IDE can used to input and compile JavaScript code for the Map Methods.

Open Source

JavaScript follows the ECMAScript standard and is licensed under the W3C Software License by web browser vendors and runtime environment vendors. This allows commercial use, modification, distribution, and allows making derivatives proprietary.

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Conclusion:

JavaScript makes it easy to create Maps and use Map Methods. Map are used to store key-value pairs of any data type and Map Methods manipulate elements and values.

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References:

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• Learning Python Ebook on Amazon
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