js array fill() filling method

Preface:

We know a lot about how to initialize arrays, but after initializing the array, each element in the array defaults to an empty placeholder. How can we add default elements to these empty places in the array? ES6 provides fill() method to achieve this operation. This article summarizes the detailed use of the array fill() method.

1. fill() syntax

fill() method fills all elements in an array from the start index to the end index with a fixed value. The ending index is not included. Returns the original array modified without creating a new array.

Use the syntax: array.fill( value [,start [,end]])， where:

• value is used to fill the value of array elements, required.
• start is an optional starting index, the default value is 0.
• end optional ending index, defaults to this.length .

2. Use of fill()

   // When a single parameter is passed, the method fills the entire array with the value of that parameter var arr1 = new Array(5)
    console.log(arr1.fill(1)); //[1,1,1,1,1]
    var arr2 = [1, 2, 3, 4]
    console.log(arr2.fill(0)); //[0,0,0,0]

    // When two parameters are passed in, the first parameter is the element to be filled, and the second is the starting position of the filled element var arr3 = [0, 1, 2, 3, 4, 5, 6]
    console.log(arr3.fill(1, 3)); //[0,1,2,1,1,1,1]

    // When three parameters are passed in, the first parameter is the element to be filled, the second and third parameters refer to the starting and ending positions of the filled element respectively, and the ending position element is not modified var arr4 = [0, 1, 2, 3, 4, 5]
    console.log(arr4.fill(1, 3, 5)); //[0,1,2,1,1,5]
    
    //If the starting position or ending position provided is a negative number, the length of the array will be added to them to calculate the final position. For example, a starting position of -1 is equivalent to array.length-1
    var arr5 = [0, 1, 2, 3, 4, 5]
    console.log(arr5.fill(1, -3));//[0,1,2,1,1,1]
    var arr6 = [0, 1, 2, 3, 4, 5]
    console.log(arr6.fill(1, 3, -2));//[0,1,2,1,4,5]

3. Summary

The above is the full content of this article. I hope it can bring some help and progress to the readers. If it is convenient, please follow me. Xiaobai’s Growth Path will continue to update some common problems and technical points in work.

This is the end of this article about the js array fill() filling method. For more related js array fill() filling content, please search for previous articles on 123WORDPRESS.COM or continue to browse the following related articles. I hope everyone will support 123WORDPRESS.COM in the future!