Explain the functions of substring and substr intercepted by using explain script

There are two major substring and substr functions in javascript For string truncation. Next I will introduce the usage of the two string interceptions respectively. If you need to know about them, refer.

I. substring

Substring requires at least one parameter. The first parameter is the starting position, and the second parameter is optional. It is the ending position.

Only one parameter

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<Meta charset = "UTF-8"/> <Script type = 'text/javascript '> /** * Substring function DEMO */ Var str = 'Welcome to the qiongtai blog '; Var sub = str. substring (3 ); Alert (sub); // out: Visit the qiongtai blog </Script>

Two Parameters

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<Meta charset = "UTF-8"/> <Script type = 'text/javascript '> /** * Substring function DEMO */ Var str = 'Welcome to the qiongtai blog '; Var sub = str. substring (3,11 ); Alert (sub); // out: Enter the qiongtai blog </Script>

Ii. substr

Substr also requires at least one parameter. The first parameter is the starting position, and the second parameter is optional, which is the length.

Only one parameter

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<Meta charset = "UTF-8"/> <Script type = 'text/javascript '> /** * Substring function DEMO */ Var str = 'Welcome to the qiongtai blog '; Var sub = str. substr (3 ); Alert (sub); // out: Visit the qiongtai blog </Script>

 
Two Parameters

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<Meta charset = "UTF-8"/> <Script type = 'text/javascript '> /** * Substring function DEMO */ Var str = 'Welcome to the qiongtai blog '; Var sub = str. substr (3, 2 ); Alert (sub); // out: a child </Script>

As shown in the preceding example, the results of substring and substr are the same only when there is only one parameter.

Other functions

Function: split ()
Function: uses a specified separator to split a string and store it in an array.
Example:

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Str = "jpg | bmp | gif | ico | png "; Arr = theString. split ("| "); // Arr is an array containing character values "jpg", "bmp", "gif", "ico", and "png"

Function: John ()
Function: combines an array into a string using the separator you selected.
Example:

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Var delimitedString = myArray. join (delimiter ); Var myList = new Array ("jpg", "bmp", "gif", "ico", "png "); Var portableList = myList. join ("| ");

// The result is jpg | bmp | gif | ico | png.

Function: indexOf ()
Function: returns the subscript of the first character matching the substring in a string.

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Var myString = "JavaScript "; Var w = myString. indexOf ("v"); w will be 2 Var x = myString. indexOf ("S"); x will be 4 Var y = myString. indexOf ("Script"); y will also be 4 Var z = myString. indexOf ("key"); z will be-1

Example

Example:

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<Script type = "text/javascript"> Var str = "0123456789 ";// Alert (str. substring (0); // ------------ "0123456789" Alert (str. substring (5); // ------------ "56789" Alert (str. substring (10 ));//-----------"" Alert (str. substring (12 ));//-----------"" Alert (str. substring (-5); // ----------- "0123456789" Alert (str. substring (-10); // ---------- "0123456789" Alert (str. substring (-12); // ---------- "0123456789" Alert (str. substring (0, 5); // ---------- "01234" Alert (str. substring (0, 10); // --------- "0123456789" Alert (str. substring (0, 12); // --------- "0123456789" Alert (str. substring (2, 0); // ---------- "01" Alert (str. substring (2, 2 ));//----------"" Alert (str. substring (2, 5); // ---------- "234" Alert (str. substring (2,12); // --------- "23456789" Alert (str. substring (2,-2); // --------- "01" Alert (str. substring (-1, 5); // --------- "01234" Alert (str. substring (-1,-5 ));//--------"" Alert (str. substr (0); // --------------- "0123456789" Alert (str. substr (5); // --------------- "56789" Alert (str. substr (10 ));//--------------"" Alert (str. substr (12 ));//--------------"" Alert (str. substr (-5); // -------------- "0123456789" Alert (str. substr (-10); // ------------- "0123456789" Alert (str. substr (-12); // ------------- "0123456789" Alert (str. substr (0, 5); // ------------- "01234" Alert (str. substr (0, 10); // ------------ "0123456789" Alert (str. substr (0, 12); // ------------ "0123456789" Alert (str. substr (2, 0 ));//-------------"" Alert (str. substr (2, 2); // ------------- "23" Alert (str. substr (2, 5); // ------------- "23456" Alert (str. substr (2, 12); // ------------ "23456789" Alert (str. substr (2,-2 ));//------------"" Alert (str. substr (-1, 5); // ------------ "01234" Alert (str. substr (-1,-5 ));//-----------"" </Script>