Use of built-in function Map in JavaScript

JavaScript is a dynamic, interpretive programming language used to develop dynamic pages and interactive applications on the web. Compared with other programming languages, JavaScript has more flexible built-in data types and has higher levels of debugging and error handling tools. One of the core features of JavaScript is its built-in Map() data structure. This article will introduce Map() in JavaScript in detail.

Definition and basic use of Map()

Map() is a data structure built into JavaScript that allows you to map key-value pairs to values of any type. Map() is very simple to use, you can create a new Map() instance in the following ways.

const myMap = new Map();

Now you can add elements to Map() using the set() method. The set() method accepts two parameters: key and value.

("key1", "value1");
("key2", "value2");

Here, we map the strings "key1" and "key2" to the values "value1" and "value2" respectively.

To retrieve a value from Map(), you can use the get() method, which accepts a key as an argument.

(("key1")); //Output："value1"

If you want to get all keys or all values in Map(), you can use the keys() or values() method to return an iterator.

([...()]); //Output: ["key1", "key2"]([...()]); //Output：["value1", "value2"]

Advanced features of Map()

In addition to basic addition and retrieval of elements, Map() provides some other powerful features that are very useful in some cases.

Any type can be used as keys

Unlike objects, Map() can use any type as a key, including functions, arrays, objects, or even other Map() instances. This makes Map() very flexible.

const myFunc = () =&gt; ("Hello World!");
const myArray = [1, 2, 3];
const myObject = {name: "John Doe", age: 30};
const myMap = new Map();
(myFunc, "Function value");
(myArray, "Array value");
(myObject, "Object value");
((myFunc)); //Output: "Function value"((myArray)); //Output: "Array value"((myObject)); //Output："Object value"

Easy to iterate over all elements

Map() provides an entries() method that returns an iterator that contains key/value pairs of all elements in Map().

for (let [key, value] of ()) {
  (key, value);
}
//Output://myFunc() "Function value"
//[1, 2, 3] "Array value"
//{name: "John Doe", age: 30} "Object value"

Easy to detect whether the element exists

Map() provides a has() method that accepts a key and returns a boolean value indicating whether the key exists in Map().

((myFunc)); //Output: true(("non-existent key")); //Output：false

Easily delete elements

Similar to the set() method, Map() also has a delete() method that can be used to delete a specified key and its associated value from Map().

(myFunc);
((myFunc)); //Output：false

Have extensible properties and methods

The Map() object is extensible and allows you to override any attribute or method to suit your needs. For example, you can extend Map() to include a "clear()" method.

class MyMap extends Map {
  clear() {
    ("Clearing the map!");
    ();
  }
}
const myMap = new MyMap();
("key1", "value1");
("key2", "value2");
(); //Output："Clearing the map!"

Map() usage scenarios

While Map() may not be as common as other JavaScript data structures such as objects or arrays, it is very practical in some cases.

Cache data

Map() is great for use as a cache because the underlying data structure of key/value pairs is very fast and easy to retrieve and update.

const cache = new Map();
function getSomeData(id) {
  if ((id)) {
    return (id);
  } else {
    const data = fetchDataFromServer(id);
    (id, data);
    return data;
  }
}

Loop with keys

Map() makes it very easy to use keys during a loop, which is very useful when you need to traverse multiple arrays or objects.

const myMap = new Map();
("key1", "value1");
("key2", "value2");
for (let [key, value] of myMap) {
  (key, value);
}
//Output://key1 "value1"
//key2 "value2"

Translate text

Map() allows for fast and customizable text translation. Put all text in one Map() and select the corresponding translation of the key according to the current language.

const translations = new Map([
  ["Hello", {
    "en-US": "Hello",
    "zh-CN": "Hello",
    "fr-FR": "Bonjour"
  }],
  ["Goodbye", {
    "en-US": "Goodbye",
    "zh-CN": "goodbye",
    "fr-FR": "Au revoir"
  }]
]);
function translate(text, language) {
  return (text)[language];
}
(translate("Hello", "zh-CN")); //Output："Hello"

in conclusion

Map() is a fast and flexible data structure in JavaScript that supports any type of keys and extensible properties and methods. It is very practical in many cases, including cached data, loops with keys, and text translation. If you need a fast and flexible data structure to store and retrieve key-value pairs, consider using Map() in JavaScript.

This is the end of this article about the use of the built-in function Map() in JavaScript. For more related JavaScript Map() content, please search for my previous articles or continue browsing the related articles below. I hope everyone will support me in the future!