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This article introduces the relevant knowledge of "the definition and usage of substring and substr methods in javascrip". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

1.substring method

Definition and usage

The substring method is used to extract characters that are mediated between two specified subscripts.

Grammar

StringObject.substring (start,stop)

Parameter description

Start is required. A non-negative integer that specifies the position of the first character of the substring to be extracted in the stringObject.

Stop is optional. A non-negative integer that is 1 more positioned in stringObject than the last character of the substring to be extracted. If this parameter is omitted, the substring returned will go all the way to the end of the string.

Return value

A new string whose value contains a substring of stringObject whose contents are all characters from start to stop-1, whose length is stop minus start.

Description

The substring returned by the substring method includes the character at start, but not the character at end.

If start is equal to end, then the method returns an empty string (that is, a string of length 0).

If start is larger than end, the method swaps these two parameters before extracting the substring.

If start or end is negative, it will be replaced with 0.

2.substr method

Definition and usage

The substr method is used to return a substring of the specified length starting at the specified location.

Grammar

StringObject.substr (start [, length])

Parameter description

Start is required. The starting position of the required substring. The index of the first character in the string is 0.

Length is optional. The number of characters that should be included in the returned substring.

Description

If length is 0 or a negative number, an empty string is returned.

If this parameter is not specified, the substring continues to the end of the stringObject.

For example:

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 (0P5));-"01234"

Alert (str.substring (0J10));-"0123456789"

Alert (str.substring (0J12));-"0123456789"

Alert (str.substring (2J0));-"01"

Alert (str.substring (2));-"

Alert (str.substring (2) 5);-"234"

Alert (str.substring (2) 12);-"23456789"

Alert (str.substring (2memmur2));-"01"

Alert (str.substring (- 1pr 5));-"01234"

Alert (str.substring (- 1));-"

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 (0P5));-"01234"

Alert (str.substr (0J10));-"0123456789"

Alert (str.substr (0J12));-"0123456789"

Alert (str.substr (2. 0));-"

Alert (str.substr (2));-"23"

Alert (str.substr (2) 5);-"23456"

Alert (str.substr (2) 12);-"23456789"

Alert (str.substr (2mai muri 2));-"

Alert (str.substr (- 1pr 5));-"01234"

Alert (str.substr (- 1));-"

References:

Http://www.w3school.com.cn/js/jsref_substring.asp

Http://www.w3school.com.cn/js/jsref_substr.asp

3. IndexOf (String.indexOf method)

The IndexOf () method of a string searches for whether a string passed as an argument appears on the string, and returns the starting position of the character if it is found (0 for the first character, 1 for the second character, and so on) if not found, returns-1

Returns the character position of the first occurrence of the substring in the String object.

Public indexOf (value:String, [startIndex:Number]): Number

Searches for the string and returns the location of the first occurrence of the value found at or after the startIndex position within the calling string. This index starts at zero, which means that the first character in the string is considered to be at index 0 instead of index 1. If it is not found

Value, which returns-1.

Parameters.

Value:String-A string; a substring to search for.

StartIndex:Number [optional]-an integer that specifies the starting index of the search.

That's all for the definition and usage of substring and substr methods in javascrip. Thank you for reading. If you want to know more about the industry, you can follow the website, the editor will output more high-quality practical articles for you!

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