The role of function in js

The role of function in JavaScript is to define reusable blocks of code to perform specific tasks, encapsulate data and logic, and accept parameters and return results. Specifically: Define reusable code blocks. Perform specific tasks. Encapsulate data and logic. Accepts parameters and returns results.

The role of function in JavaScript

In JavaScript, the function keyword is used to define a function. A function is an independent block of code that can be called multiple times and can receive parameters and return results.

Specifically, the role of function is mainly reflected in the following aspects:

Define reusable code blocks

Function allows us to repeat Organize specific or complex code into independent modules to improve code reusability. For example:

<code class="javascript">function calculateArea(length, width) {
  return length * width;
}</code>

After creating this function, we can use it anywhere in the program to calculate the area of ​​a rectangle without having to rewrite the calculation code.

Perform specific tasks

Function can be called to perform specific tasks. For example, the following function can convert a string to uppercase letters:

<code class="javascript">function toUpperCase(string) {
  return string.toUpperCase();
}</code>

After calling the toUpperCase function, we can convert a lowercase string to uppercase as follows:

<code class="javascript">const upperCaseString = toUpperCase('hello'); // 输出：HELLO</code>

Encapsulating data and logic

Function can encapsulate data and logic in an independent code block, thereby improving the organization and modularity of the code. For example, the following function can represent a user object:

<code class="javascript">function User(name, age) {
  this.name = name;
  this.age = age;
  this.greet = function() {
    console.log('Hello, my name is ' + this.name);
  }
}</code>

This function encapsulates user data (name and age) and the logic of accessing the data (greet method) to facilitate management and replication. use.

Accepting parameters and returning results

Function can accept parameters and perform different operations based on these parameters. For example, the following function calculates the sum of two numbers:

<code class="javascript">function add(num1, num2) {
  return num1 + num2;
}</code>

When calling the add function, we can pass the numbers to be added and get their sum:

<code class="javascript">const result = add(10, 20); // 输出：30</code>

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