javascript basic methods

JavaScript is a widely used programming language mainly used for front-end web development. It provides various methods and functions that allow developers to easily add dynamic interactivity and functionality to web pages. This article will introduce some basic methods of JavaScript.

I. Variables

In JavaScript, variables are containers used to store data. Variables can be defined using the var, let or const keywords, which are used to declare mutable variables, block-scope variables and constants respectively.

Syntax:
var variable_name = value;
or
let variable_name = value;
or
const variable_name = value;

II. Operator

JavaScript supports various types of operators, including arithmetic, assignment, comparison, logical, bitwise and ternary operators, etc. Common operators are shown in the following table:

III. Conditional Statement

Conditional statement is used to execute a specific block of code when certain conditions are met. JavaScript supports if, else and switch statements.

The syntax of the if statement is as follows:
if (condition) {
// If condition is true, execute this part of the code
}

if...else statement The syntax is as follows:
if (condition) {
// If condition is true, execute this part of the code
} else {
// If condition is false, execute this part of the code
}

The syntax of the switch statement is as follows:
switch (expression) {
case value1:

// 如果表达式的值等于 value1，执行该部分代码 break;

case value2:

// 如果表达式的值等于 value2，执行该部分代码 break;

default:

// 如果表达式的值不等于任何一个值，执行该部分代码 break;

}

IV. Loop statement

Loop statement is a statement used to repeatedly execute a block of code. JavaScript supports for, while and do...while statements.

The syntax of the for loop is as follows:
for (initialization; condition; increment/decrement) {
// Loop code block
}

The syntax of the while loop is as follows:
while (condition) {
// Loop code block
}

do...The syntax of the while loop is as follows:
do {
// Loop code block
} while (condition);

V. Function

A function is a reusable block of code that performs a specific task. Functions can be defined using the function keyword.

The syntax of the function is as follows:
function function_name(parameter1, parameter2, ...) {
// Function code block
return value;
}

VI. Object

Object is a data type composed of properties and methods. In JavaScript, all objects are instances of built-in objects such as Array, Date, Math, and String.

The syntax of the object is as follows:
var object_name = {property1: value1, property2: value2, ...};

You can use the . and [] operators to access the properties of the object and methods.

VII. Array

An array is an object used to store a set of ordered data. Arrays can be defined using the [] or Array() constructor.

The syntax of the array is as follows:
var array_name = [value1, value2, ...];

You can use index to access the elements in the array, for example:
var fruits = ["apple", "banana", "orange"];
console.log(fruits[0]); // Output "apple"

VIII. String

A string is an object used to represent text data. Strings can be defined using '' or "" or `` brackets.

The syntax of string is as follows:
var string_name = 'string_value';

You can use operators to connect multiple strings, for example:
var first_name = "John" ;
var last_name = "Doe";
var full_name = first_name " " last_name;
console.log(full_name); // Output "John Doe"

The above are some JavaScript Basic methods and syntax. Learning and mastering these methods and syntax will be of great help for a deeper understanding and application of the JavaScript programming language.

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