How to delete array elements and clear arrays using javascript

This article describes how to delete array elements in javascript and how to clear arrays, for more information about how to delete array elements and clear arrays, see the next article.

Simple Method for deleting array elements and clearing arrays using javascript

I. Clear the Array

Var ary = [1, 2, 4]; ary. splice (0, ary. length); // clear the array console. log (ary); // output [], empty array, which is cleared

Ii. Delete array elements

Var ary = [1, 2, 4]; ary. splice (0, 1); or ary. splice ($. inArray (2, ary), 1); where $. inArray (2, ary) is used to find the index position of an element in the array.

3. Several Methods for deleting arrays in js

var arr=[‘a','b','c'];

To delete 'B', you can use either of the following methods:

** 1, ** delete method: delete arr [1]

In this way, the length of the array remains unchanged. In this case, the arr [1] is changed to undefined, but the index of the original array remains unchanged. In this case, you need to traverse the array element before using it.

for(index in arr){ document.write('arr['+index+']='+arr[index]);}

This Traversal method skips the undefined element.

* IE4.o is supported later.

2. array object splice method: arr. splice );

In this way, the length of the array is changed, but the original array index is also changed.

The first 1 in the splice parameter is the initial index to be deleted (from 0), and the second element of the array.

The second one is the number of elements deleted. Only one element is deleted here, that is, 'B ';

In this case, the elements in the array can be traversed in the normal way, for example, because the deleted elements are

The array is not retained.

This method is supported only after IE5.5.
It is worth mentioning that the splice method can also add array elements while deleting array elements.

For example, arr. splice (, 'D', 'E'), d, and e are added to the array arr.

The result array is changed to arr: 'A', 'D', 'E', 'c'

In addition, JavaScript truncates an array by setting the length attribute of the array, which is the only method to shorten the length of the array.

If you use the delete operator to delete elements in an array, although the element becomes undefined, The length attribute of the array does not change the two ways to delete elements, and the length of the array also changes.

/** Method: Array. remove (dx) * function: delete array elements. * parameter: dx deletes the subscript of an element. * return: Modify the array on the original array * // It is often used to traverse and reconstruct the array. array. prototype. remove = function (dx) {if (isNaN (dx) | dx> this. length) {return false;} for (var I = 0, n = 0; I
 
  

  


  

  
/** Method: Array. baoremove (dx) * function: delete array elements. * parameter: dx deletes the subscript of an element. * return value: Modify the array on the original array. * /// you can also use splice. array. prototype. baoremove = function (dx) {// www. jb51.netif (isNaN (dx) | dx> this. length) {return false;} this. splice (dx, 1);} B = ['1', '2', '3', '4', '5']; alert ("elements: "+ B +" nLength: "+ B. length); B. baoremove (1); // Delete alert ("elements:" + B + "nLength:" + B. length );
  

  
In IE5 or earlier versions, the Array (Array) object of JavaScript does not provide a ready-to-use method to delete Array elements. In IE5.5 + versions, although there is a splice method, it does not delete one or more items, but simply clears the value of one or more items, that is to say, this item still exists, and the length of the array has not changed.
  
In fact, you can add a deletion method for the array by yourself (note that this refers to removing a certain item of the array from the array member ). Perhaps, you may think of repeating the array to re-assign values. This is certainly possible, but the efficiency is very low.
  
The following describes how to use two methods of the Array object: slice and concat to customize the method for deleting arrays.
  

  
Array. prototype. del = function (n) {// n indicates the number of items, starting from 0. // Prototype is the object prototype. Note that the custom method is added for the object. If (n <0) // if n <0, no operation is performed. Return this; elsereturn this. slice (0, n ). concat (this. slice (n + 1, this. length);/* concat method: returns a new array consisting of two or more arrays. Here is a new array consisting of this. slice (0, n)/this. slice (n + 1, this. length). In the middle, the nth entry is missing. Slice Method: return a segment of an array with two parameters, respectively specifying the start and end positions. * // Method var test = new Array (,); test = test. del (3); // Delete 4th items from 0. Alert (test );
  

  
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