javascript array delete item

JavaScript is a very popular programming language that is widely used in web development. Arrays are a very common data structure in JavaScript. The elements in the array can be various types of data, such as numbers, strings, objects, etc. In actual development, we often need to operate on arrays, one of which is to delete certain items in the array. This article will introduce several commonly used methods to delete items from JavaScript arrays.

1. Use the splice() method

The splice() method is a very commonly used array method in JavaScript, which can modify the contents of the array. The syntax of the splice() method is as follows:

array.splice(start, deleteCount[, item1[, item2[, ...]]])

This method accepts three parameters. One parameter represents the starting position to be deleted, the second parameter represents the number of elements to be deleted, and the third and subsequent parameters represent the insertion of one or more new elements at the deleted position. If you do not specify the third parameter and subsequent parameters, the splice() method will only delete elements and not insert new elements.

For example, to delete the 3rd element in the array arr, you can use the following code:

let arr = ['a', 'b', 'c', 'd', 'e'];
arr.splice(2, 1);
console.log(arr); // 打印结果：['a', 'b', 'd', 'e']

The first parameter in the above code is 2, which means that the starting position to be deleted is The third element (array subscript starts from 0), the second parameter is 1, indicating that the number of elements to be deleted is 1.

2. Use slice() method and concat() method

In addition to using splice() method, we can also use slice() method combined with concat() method, to delete certain items from the array. The slice() method can return the element at the specified position, while the concat() method can add the specified array or element to the end of the current array. The syntax is as follows:

array.slice(start, end)

array.concat(item1[, item2[, ...]])

Among them, slice( ) method accepts two parameters, the first parameter indicates the starting position of the element to be returned, and the second parameter indicates the end position of the element to be returned. If the second parameter is not specified, it means that all elements from the starting position to the end of the array are returned. The concat() method can accept any number of parameters, indicating new elements to be added to the current array.

The following code demonstrates how to use the slice() method and concat() method to delete specified elements in the array:

let arr = ['a', 'b', 'c', 'd', 'e'];
let newArr = arr.slice(0, 2).concat(arr.slice(3));
console.log(newArr); // 打印结果：['a', 'b', 'd', 'e']

In the above code, first use slice(0, 2) to return Elements with a starting position of 0 and an ending position of 2 (i.e., the first two elements in the array), and then use the concat() method to add the remaining elements (i.e., the 3rd element and subsequent elements) to the new array , thereby achieving the effect of deleting elements.

3. Use the filter() method

The filter() method in JavaScript can filter the array according to the specified conditions and return a new array composed of elements that meet the conditions. . Therefore, we can use the filter() method to remove certain items from the array. The specific implementation method is as follows:

let arr = ['a', 'b', 'c', 'd', 'e'];
let newArr = arr.filter(function(element) {
  return element !== 'c';
});
console.log(newArr); // 打印结果：['a', 'b', 'd', 'e']

In the above code, the callback function of the filter() method will be passed each element in the array and add the elements that meet the conditions to the new array. In this example, we want to delete element 'c' from the array, so the callback function returns element !== 'c', which means that as long as the element is not equal to 'c', add it to the new array.

Summary

This article introduces several methods commonly used in JavaScript to delete items from arrays, including using the splice() method, using the slice() method in combination with the concat() method, and using filter( ) method. Each method has its applicable scenarios and usage, and you need to flexibly choose according to the actual situation when using it. In actual development, we often need to perform operations such as adding, deleting, modifying, and checking arrays, so it is very important to understand and master the related methods of arrays in JavaScript.

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