Please tell me the understanding of the unshift and push methods in js
In JavaScript,unshiftandpushare two commonly used methods of arrays, which are used to add elements at the beginning and end of an array respectively. Both methods are methods to change the original array, which means that they will directly modify the original array rather than create a new array.
- push method
pushThe method adds one or more elements to the end of the array and returns the new array length. For example:
let arr = [1, 2, 3]; let length = (4, 5); (arr); // Output: [1, 2, 3, 4, 5](length); // Output: 5，Because the new length of the array is5
In this example,pushMethods add 4 and 5 to the arrayarrend and return the new array length 5.
- unshift method
unshiftThe method adds one or more elements to the beginning of the array and returns the new array length. For example:
let arr = [1, 2, 3]; let length = (0, -1); (arr); // Output: [-1, 0, 1, 2, 3](length); // Output: 5，Because the new length of the array is5
In this example,unshiftMethods add -1 and 0 to the arrayarrstarts with and returns the new array length 5.
Summarize：
-
pushandunshiftAll are methods to change the original array. -
pushAdd elements at the end of the array, andunshiftAdd elements at the beginning of the array. - Both methods return the new array length.
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