Javascript array operation function summary_javascript skills

This article mainly summarizes and introduces Javascript array operation functions. For more information, see push and pop, which are usually used, for later use.

Shift: Delete the first entry of the original array and return the value of the deleted element. If the array is empty, undefined is returned.

The Code is as follows:

Var a = [1, 2, 3, 4, 5];
Var B = a. shift (); // a: [2, 3, 4, 5] B: 1

Unshift: Add the parameter to the beginning of the original array and return the length of the array.

The Code is as follows:

Var a = [1, 2, 3, 4, 5];
Var B = a. unshift (-2,-1); // a: [-2,-,] B: 7

Note: In IE6.0, the test return value is always undefined, and in FF2.0, the test return value is 7. Therefore, the return value of this method is unreliable. You need to use splice instead of this method when returning the value. This article is from www.45it.com

Pop: Delete the last entry of the original array and return the value of the deleted element. If the array is empty, undefined is returned.

The Code is as follows:

Var a = [1, 2, 3, 4, 5];
Var B = a. pop (); // a: [1, 2, 3, 4] B: 5

Push: Add the parameter to the end of the original array and return the length of the array.

The Code is as follows:

Var a = [1, 2, 3, 4, 5];
Var B = a. push (6, 7); // a: [1, 2, 3, 4, 5, 6, 7] B: 7

Concat: Returns a new array consisting of adding parameters to the original array.

The Code is as follows:

Var a = [1, 2, 3, 4, 5];
Var B = a. concat (6, 7); // a: [1, 2, 3, 4, 5] B: [1, 2, 3, 4, 5, 7]

Splice(Start, deleteCount, val1, val2,...): Delete the deleteCount item from the start position, and insert val1, val2 ,...

The Code is as follows:

Var a = [1, 2, 3, 4, 5];
Var B = a. splice (, 9); // a: [,] B: []
Var B = a. splice (0, 1); // same as shift
A. splice (0, 0,-2,-1); var B = a. length; // same as unshift
Var B = a. splice (a. length-1, 1); // same as pop
A. splice (a. length, 7); var B = a. length; // same as push

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Splice details:

The splice function removes one or more elements from an array. If necessary, insert a new element to the position of the removed element and return the removed element.

ArrayObj. splice (start, deleteCount, [item1 [, item2 [,... [, itemN])

ArrayObj is required. An Array object.

Start is required. Specifies the start position of the element to be removed from the array. This position is calculated from 0.

DeleteCount is required. The number of elements to be removed.

Item1, item2,..., itemN is required. The new element to be inserted at the position of the removed element.

In JavaScript, the splice function can remove a specified number of elements starting from the start position and insert new elements to modify arrayObj. The returned value is a new Array object consisting of the removed elements.

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Reverse: Returns the reverse order of arrays.

The Code is as follows:

Var a = [1, 2, 3, 4, 5];
Var B = a. reverse (); // a: [5, 4, 3, 2, 1] B: [5, 4, 3, 2, 1]

Sort (orderfunction ):Sorts arrays by specified parameters

The Code is as follows:

Var a = [1, 2, 3, 4, 5];
Var B = a. sort (); // a: [1, 2, 3, 4, 5] B: [1, 2, 3, 4, 5]

Slice (start, end ):Returns a new array consisting of items from the specified start subscript to the end subscript in the original array.

The Code is as follows:

Var a = [1, 2, 3, 4, 5];
Var B = a. slice (); // a: [, 5] B: [, 5]

Join (separator ):Groups the elements of the array into a string with the separator. If this parameter is omitted, the Delimiter is separated by commas by default.

The Code is as follows:

Var a = [1, 2, 3, 4, 5];
Var B = a. join ("|"); // a: [1, 2, 3, 4, 5] B: "1 | 2 | 3 | 4 | 5"

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