As a front-end developer, having a solid foundation of JavaScript syntax and functions is essential. In this article, we'll cover over 100 commonly-used JavaScript functions and syntax, with detailed explanations and practical examples.
Basic Syntax
Variables
Variables are used to store data in JavaScript. There are three keywords to declare a variable: var, let, and const.
// Declare a variable using var var myVar = "Hello World"; // Declare a variable using let (block-scoped) let myLet = "Hey there!"; // Declare a variable using const (also block-scoped) const myConst = "Hi!";
Data Types
JavaScript has six primitive data types: string, number, boolean, null, undefined, and symbol. Objects are another type in JavaScript.
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Operators
Operators are used to perform actions on variables and values. Some common operators in JavaScript include:
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Control Flow
Control flow statements are used to control the order in which statements are executed. Common control flow statements include if-else, for, while, and switch.
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-Functions
Functions are blocks of code that can be called to perform a specific task. They can also accept parameters and return values.
Function Declaration
function sayHello() {
console.log("Hello!");
}
sayHello(); // "Hello!"Function Parameters
function greet(name) {
console.log(`Hello, ${name}!`);
}
greet("John"); // "Hello, John!"Function Return Values
function add(x, y) {
return x + y;
}
let sum = add(2, 3);
console.log(sum); // 5Arrow Functions
Arrow functions are a concise way to write functions in JavaScript.
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Higher-Order Functions
Higher-order functions are functions that accept other functions as arguments or return functions as values.
function multiplyBy(factor) {
return function (number) {
return number * factor;
};
}
const double = multiplyBy(2);
console.log(double(5)); // 10Arrays
Arrays are used to store collections of data in JavaScript. They can be of any data type and can be accessed by index.
Array Declaration
let myArray = ["apple", "banana", "orange"];
Accessing Array Elements
来源：JavaScript中文网 ，转载请注明来源 https://www.javascriptcn.com/post/2000