Summary of methods to get the last element of an array in JavaScript

There are many options when you need to get the last element from an array in JavaScript, and this article will provide 3 methods available.

1. Array length property

​​length​​ attribute returns the number of elements in the array. Subtract from the length of the array​1​​ Get the index of the last element of the array, and use it to access the last element. Subtract from length​1​The reason for this is that in JavaScript, the array index number is from​0​​ Start. That is, the index of the first element will be​0​​. Therefore, the index of the last element will be the array's​length-1​​。

const arrayTest = ["First Element", "Second Element", "The Last Element"];
const length = ;
const lastValue = arrayTest[length - 1];
(lastValue); // The last element

2. Array slice method

​​slice()​The method returns a specific element from an array as a new array object. This method selects elements from the given start index to the end of the given end index, excluding the elements at the end index. ​​slice()​The method does not modify the existing array, provides an index value to return the element at that position, and the negative index value calculates the index from the end of the array. The deconstructed assignment of array matching is used to​slice()​​ Get elements from the array returned by the method.

const arrayTest = ["First Element", "Second Element", "The Last Element"];
const length = ;
const [lastValue] = (-1);
(lastValue); // The last element

3. Array pop method

​​pop()​The method deletes the last element from the array and returns it,This method will modify the original array. If the array is empty, return​undefined​And do not modify the array.

const arrayTest = ["First Element", "Second Element", "The Last Element"];
const length = ;
const lastValue = ();
(lastValue); // The last element(arrayTest); // [ 'First Element', 'Second Element' ]

Performance comparison

Let's compare these 3 methods by performance.

const arrayTest = ["First Element", "Second Element", "The Last Element"];

("==> length");
const length = ;
let lastValue = arrayTest[length - 1];
(lastValue);
("==> length");

("====> slice");
let [lastValue1] = (-1);
(lastValue1);
("====> slice");

("======> pop");
let lastValue2 = ();
(lastValue2);
("======> pop");

The output results are as follows:

The last element
==> length: 6.38ms
The last element
====> slice: 0.038ms
The last element
======> pop: 0.033ms

Summarize

​​pop()​The method is the fastest, if you can modify the array, you can use it. If you don't want to change the array, you can use​slice()​Method. The method of using the length attribute of the array is the slowest, and is the most commonly used method to obtain the last element of the array.

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