Insert an element at a specified position in a specific index of the JS array. js Array

Insert an element at a specified position in a specific index of the JS array. js Array

Many array-related tasks sound simple, but they are not always the case, and developers often do not use them. Recently, I encountered the following requirement: insert an element to a specific index of an existing array. It sounds easy and common, but it takes some time to study it.

// Original array var array = ["one", "two", "four"]; // splice (position, numberOfItemsToRemove, item) // concatenation function (index location, number of elements to be deleted, element) array. splice (2, 0, "three"); array; // The current array looks like this ["one", "two", "three", "four"]

If you are not disgusted with the extension of native JavaScript, you can add this method to the Array prototype:

Array.prototype.insert = function (index, item) { this.splice(index, 0, item); };

In this case, you can call:

Var nums = ["one", "two", "four"]; nums. insert (2, 'three '); // note the array index, [, 2 ..] array // ["one", "two", "three", "four"]

Js deletes the element of a specified value (not a specified position) from the array.

If you do not use a third-party framework, a similar extension function can return the subscript of an element based on the specified value. You can only search for the element and then delete it.

<Script type = "text/javascript">
Array. prototype. indexOf = function (val ){
For (var I = 0; I <this. length; I ++ ){
If (this [I] = val) return I;
}
Return-1;
};
Array. prototype. remove = function (val ){
Var index = this. indexOf (val );
If (index>-1 ){
This. splice (index, 1 );
}
};

Var array = [1, 2, 3, 4, 5];
Array. remove (3 );

</Script>

Js to obtain the string index of array elements ,~

Var array = new Array ();
Array [0] = "1 ";
Array [1] = "2 ";
Array [2] = "3 ";
Var index = array. length;
For (var I = 0; I <index; I ++ ){
Document. writeln (the index of array [I] + "is:" + I );
}