Detailed explanation of common methods of JavaScript String

1. charAt

Returns the specified character from a string

grammar

str.charAt(index)

parameter

index

An integer between 0 and the length of the string minus 1. (0~length-1)

If no index is provided, charAt() will use 0.

Return Value

Returns the specified character, or an empty string if the specified index value is out of range.

2. concat

Concatenates one or more strings with the original string to form a new string and returns it. The concat method does not affect the original string.

grammar

str.concat(str2, [, ...strN])

parameter

str2 [, …strN]

The string to be concatenated to str.

Return Value

A new string containing the connection string provided as a parameter.

3. indexOf

Returns the index of the first occurrence of the specified character in the String object, searching from fromIndex. If the value is not found, -1 is returned.

grammar

str.indexOf(searchValue [, fromIndex])

parameter

searchValue

The string value to be searched.
If no exact string is provided, searchValue is coerced to "undefined" and the value is then searched for within the current string.

fromIndex (optional)

The number indicates where to start searching. Can be any integer, default value is 0.
If the value of fromIndex is less than 0, or greater than str.length, then the search starts at 0 and str.length respectively. (Translator's note: if the value of fromIndex is less than 0, it is equivalent to being empty; if the value of fromIndex is greater than or equal to str.length, the result will be returned directly as -1.)

Return Value

Returns the index of the first occurrence of the search string searchValue, or -1 if not found.

Special circumstances

1. If the search string searchValue is an empty string and the fromIndex value is empty, or the fromIndex value is less than the length of the search string, the return value is the same as the fromIndex value below

2. If the search string searchValue is an empty string, and the fromIndex value is greater than or equal to the length of the string, the length of the string will be returned directly

4. lastIndexOf

The opposite of indexOf, it just searches from the back to the front.

5.match

Search returns a string that matches the regular expression.

grammar

str.match(regexp)

parameter

regexp

A regular expression object. If a non-regular expression object is passed in, it will be implicitly converted to a RegExp using new RegExp(obj). If you don't give any arguments and use the match() method directly, you will get an Array containing an empty string: [""] .

Return Value

• If the g flag is used, all results matching the full regular expression will be returned, but capturing groups will not be returned.
• If the g flag is not used, only the first complete match and its associated capturing groups (Array) are returned. In this case, the returned item will have additional properties as described below.

6. replace

Returns a new string with some or all matches of pattern replaced by replacement. The pattern can be a string or a regular expression, and the replacement can be a string or a callback function to be called on each match. If pattern is a string, only the first occurrence is replaced.

The original string will not be changed.

grammar

str.replace(regexp|substr, newSubStr|function)

parameter

regexp (pattern)

A RegExp object or its literal. The content matched by this regular expression will be replaced by the return value of the second parameter.

substr (pattern)

A string that will be replaced by newSubStr. It is treated as a whole string, not a regular expression. Only the first occurrence is replaced.

newSubStr (replacement)

The string used to replace the matching part of the first parameter in the original string. Some special variable names can be interpolated in this string. See Using Strings as Parameters below.

function (replacement)

A function that creates a new substring whose return value replaces any matches of the first argument. See Specifying a function as an argument below.

Return Value

A new string with some or all of the matches in the replacement pattern replaced.

7. toLowerCase

Converts a string value to lowercase and returns

grammar

str.toLowerCase()

Return Value

A new string representing the calling string converted to lower case.

8. toUpperCase

The opposite of toLowerCase, convert to uppercase

9. Substring

Returns a subset of a string between the start index and the end index, or from the start index until the end of the string.

grammar

str.substring(indexStart[, indexEnd])

parameter

indexStart

The index of the first character to be intercepted. The character at this index position is used as the first letter of the returned string.

indexEnd

Optional. An integer between 0 and the length of the string. The characters indexed by this number are not included in the truncated string.

Return Value

A new string containing the specified portion of a given string.

Summarize

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1. charAt

Returns the specified character from a string

grammar

str.charAt(index)

parameter

index

An integer between 0 and the length of the string minus 1. (0~length-1)

If no index is provided, charAt() will use 0.

Return Value

Returns the specified character, or an empty string if the specified index value is out of range.

2. concat

Concatenates one or more strings with the original string to form a new string and returns it. The concat method does not affect the original string.

grammar

str.concat(str2, [, ...strN])

parameter

str2 [, …strN]

The string to be concatenated to str.

Return Value

A new string containing the connection string provided as a parameter.

3. indexOf

Returns the index of the first occurrence of the specified character in the String object, searching from fromIndex. If the value is not found, -1 is returned.

grammar

str.indexOf(searchValue [, fromIndex])

parameter

searchValue

The string value to be searched.
If no exact string is provided, searchValue is coerced to "undefined" and the value is then searched for within the current string.

fromIndex (optional)

The number indicates where to start searching. Can be any integer, default value is 0.
If the value of fromIndex is less than 0, or greater than str.length, then the search starts at 0 and str.length respectively. (Translator's note: if the value of fromIndex is less than 0, it is equivalent to being empty; if the value of fromIndex is greater than or equal to str.length, the result will be returned directly as -1.)

Return Value

Returns the index of the first occurrence of the search string searchValue, or -1 if not found.

Special circumstances

1. If the search string searchValue is an empty string and the fromIndex value is empty, or the fromIndex value is less than the length of the search string, the return value is the same as the fromIndex value below

2. If the search string searchValue is an empty string, and the fromIndex value is greater than or equal to the length of the string, the length of the string will be returned directly

4. lastIndexOf

The opposite of indexOf, it just searches from the back to the front.

5.match

Search returns a string that matches the regular expression.

grammar

str.match(regexp)

parameter

regexp

A regular expression object. If a non-regular expression object is passed in, it will be implicitly converted to a RegExp using new RegExp(obj). If you don't give any arguments and use the match() method directly, you will get an Array containing an empty string: [""] .

Return Value

• If the g flag is used, all results matching the full regular expression will be returned, but capturing groups will not be returned.
• If the g flag is not used, only the first complete match and its associated capturing groups (Array) are returned. In this case, the returned item will have additional properties as described below.

6. replace

Returns a new string with some or all matches of pattern replaced by replacement. The pattern can be a string or a regular expression, and the replacement can be a string or a callback function to be called on each match. If pattern is a string, only the first occurrence is replaced.

The original string will not be changed.

grammar

str.replace(regexp|substr, newSubStr|function)

parameter

regexp (pattern)

A RegExp object or its literal. The content matched by this regular expression will be replaced by the return value of the second parameter.

substr (pattern)

A string that will be replaced by newSubStr. It is treated as a whole string, not a regular expression. Only the first occurrence is replaced.

newSubStr (replacement)

The string used to replace the matching part of the first parameter in the original string. Some special variable names can be interpolated in this string. See Using Strings as Parameters below.

function (replacement)

A function that creates a new substring whose return value replaces any matches of the first argument. See Specifying a function as an argument below.

Return Value

A new string with some or all of the matches in the replacement pattern replaced.

7. toLowerCase

Converts a string value to lowercase and returns

grammar

str.toLowerCase()

Return Value

A new string representing the calling string converted to lower case.

8. toUpperCase

The opposite of toLowerCase, convert to uppercase

9. Substring

Returns a subset of a string between the start index and the end index, or from the start index until the end of the string.

grammar

str.substring(indexStart[, indexEnd])

parameter

indexStart

The index of the first character to be intercepted. The character at this index position is used as the first letter of the returned string.

indexEnd

Optional. An integer between 0 and the length of the string. The characters indexed by this number are not included in the truncated string.

Return Value

A new string containing the specified portion of a given string.

Summarize

This article ends here. I hope it can be helpful to you. I also hope you can pay more attention to more content on 123WORDPRESS.COM!