What are the methods of javascript array object

JavaScript is a programming language widely used in Internet development and supports various operations and calculations, including the definition and operation of arrays. An array is a data structure that can hold multiple values ​​and arrange them in a certain order. In order to facilitate the processing of array objects, JavaScript provides many methods of array objects. This article will introduce commonly used JavaScript array object methods and their usage.

1. join() method

The join() method puts all elements of the array into a string, and the delimiter can be specified. For example:

var fruits = ["apple", "banana", "orange"];
var result = fruits.join(", ");
console.log(result); // 输出: "apple, banana, orange"

2. concat() method

The concat() method is used to concatenate two or more arrays and return a new array. For example:

var fruits1 = ["apple", "banana"];
var fruits2 = ["orange", "lemon"];
var result = fruits1.concat(fruits2);
console.log(result); // 输出: ["apple", "banana", "orange", "lemon"]

3. push() method

push() method adds one or more elements to the end of the array and returns the new length. For example:

var fruits = ["apple", "banana"];
var length = fruits.push("orange", "lemon");
console.log(length); // 输出: 4
console.log(fruits); // 输出: ["apple", "banana", "orange", "lemon"]

4. pop() method

The pop() method removes an element from the end of the array and returns the value of the element. For example:

var fruits = ["apple", "banana", "orange"];
var lastFruit = fruits.pop();
console.log(lastFruit); // 输出: "orange"
console.log(fruits); // 输出: ["apple", "banana"]

5. shift() method

shift() method removes an element from the beginning of the array and returns the value of the element. For example:

var fruits = ["apple", "banana", "orange"];
var firstFruit = fruits.shift();
console.log(firstFruit); // 输出: "apple"
console.log(fruits); // 输出: ["banana", "orange"]

6. unshift() method

The unshift() method adds one or more elements to the beginning of the array and returns the new length. For example:

var fruits = ["banana", "orange"];
var length = fruits.unshift("apple", "lemon");
console.log(length); // 输出: 4
console.log(fruits); // 输出: ["apple", "lemon", "banana", "orange"]

7. slice() method

slice() method returns a new array containing the selected elements from start to end (excluding the end). For example:

var fruits = ["apple", "banana", "orange", "lemon"];
var newFruits = fruits.slice(1, 3);
console.log(newFruits); // 输出: ["banana", "orange"]

8. splice() method

splice() method adds/removes items to/from the array, and then returns the deleted item. For example:

var fruits = ["apple", "banana", "orange", "lemon"];
fruits.splice(1, 2, "pear", "kiwi");
console.log(fruits); // 输出: ["apple", "pear", "kiwi", "lemon"]

9. forEach() method

The forEach() method executes the specified function once for each element in the array. For example:

var fruits = ["apple", "banana", "orange", "lemon"];
fruits.forEach(function(fruit) {
  console.log(fruit);
});
// 输出: "apple"
//       "banana"
//       "orange"
//       "lemon"

10. filter() method

filter() method creates a new array that contains all elements that meet the conditions. For example:

var numbers = [1, 2, 3, 4, 5, 6];
var evenNumbers = numbers.filter(function(number) {
  return number % 2 == 0;
});
console.log(evenNumbers); // 输出: [2, 4, 6]

11. map() method

map() method creates a new array whose elements are the result of calling a function on each element of the original array. For example:

var numbers = [1, 2, 3, 4, 5];
var squareNumbers = numbers.map(function(number) {
  return number * number;
});
console.log(squareNumbers); // 输出: [1, 4, 9, 16, 25]

12. reduce() method

reduce() method accumulates all elements of the array and returns a value. For example:

var numbers = [1, 2, 3, 4, 5];
var sum = numbers.reduce(function(total, number) {
  return total + number;
});
console.log(sum); // 输出: 15

The above are common JavaScript array object methods. They make array creation and manipulation more convenient. In practice, you can choose the appropriate method according to your needs and use it for your project.

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