20241120_ String (Methods,Templates)

. length : length of a string

Extracting String Characters

.charAt(position) :  returns the character at a specified index (position)

.charCodeAt (position) :  returns a UTF-16 code 

.at (position) :  returns the character at a specified index (position) in a string.( supported in all modern browsers since March 2022 )

property Access : ex) String[position]

If no character is found, [ ] returns undefined, while charAt() returns an empty string.

 

Extracting String Parts

.slice( start,  end )  : returns the extracted part in a new string

.slice(position) : positive_ slice out the rest, negative_ slice out the end

. substring ( start,  end )  : similar to .slice(), but start and end values less than 0 are treated as 0

 

Converting to Upper and Lower Case

.toUpperCase() : converted to upper case

.toLowerCase() : converted to lower case 

 

 .concat("asdfa","asdfasdf") : joins two or more strings

.trim()  :  removes whitespace from both sides

.trimStart() : removes whitespace only from the start

.trimEnd() : removes whitespace only from the end

.padStart(lenght, String ) : string (multiple times) until it reaches a given length from the start (padStart is String method so can't use number) 

.padEnd(lenght, String ) :  string (multiple times) until it reaches a given length from the end (padEnd is String method so can't use number) 

.repeat(count) :  returns a string with a number of copies

Replacing String Content

.replace( value , new value) : replaces only the first match, case sensitive

                 To replace case insensitive, use a regular expression with an /i flag (insensitive)

                 To  replace all matches, use a regular expression with a /g flag

.replays(value, new value ) : 

 

Converting a String to an Array

string can be converted to an array with the .split() method   ex)x= 'j,e,o,n'; x.split(",") -> x = ['j','e','o','n']

 

String Search

.indexOf(value) : returns the index (position) of the first occurrence of a string in a string, or it returns -1 if the string is not found

.indexOf(value, startpoint) : if you want to select s tarting position for the search

.lastIndexOf(value) : eturns the index of the last occurrence of a specified text

.search(value) : returns the position of the match

               // .indexOf(value)  .search(value) . two methods are NOT equal. These are the differences 

               //  .search() can't select start-posittion 

.match( value ) : r eturns an array containing the results of matching a string against

.matchAll( value ) :  returns an iterator containing the results of matching a string against a string 

.includes( value ) :  returns true if a string contains a specified value( case sensitive )

.startsWith( value ) :  returns true if a string begins with a specified value

.startsWith( value, startposition ) :  start position for the search can be specified

.endsWith( value ) : returns true if a string ends with a specified value

.endsWith( value, endposition ) :  end position for the search can be specified

 

Interpolation

Template String provide an easy way to interpolate variables and expressions into strings

${...}

 

Variable Substitutions

ex )

let firstName = "John";
let lastName = "Doe";

let text = `Welcome ${firstName}, ${lastName}!`;

 

String Method~~~

at()	Returns an indexed character from a string
charAt()	Returns the character at a specified index (position)
charCodeAt()	Returns the Unicode of the character at a specified index
codePointAt()	Returns the Unicode value at an index (position) in a string
concat()	Returns two or more joined strings
constructor	Returns the string's constructor function
endsWith()	Returns if a string ends with a specified value
fromCharCode()	Returns Unicode values as characters
includes()	Returns if a string contains a specified value
indexOf()	Returns the index (position) of the first occurrence of a value in a string
lastIndexOf()	Returns the index (position) of the last occurrence of a value in a string
length	Returns the length of a string
localeCompare()	Compares two strings in the current locale
match()	Searches a string for a value, or a regular expression, and returns the matches
padEnd()	Pads a string at the end
padStart()	Pads a string from the start
prototype	Allows you to add properties and methods to an object
repeat()	Returns a new string with a number of copies of a string
replace()	Searches a string for a pattern, and returns a string where the first match is replaced
replaceAll()	Searches a string for a pattern and returns a new string where all matches are replaced
search()	Searches a string for a value, or regular expression, and returns the index (position) of the match
slice()	Extracts a part of a string and returns a new string
split()	Splits a string into an array of substrings
startsWith()	Checks whether a string begins with specified characters
substr()	Extracts a number of characters from a string, from a start index (position)
substring()	Extracts characters from a string, between two specified indices (positions)
toLocaleLowerCase()	Returns a string converted to lowercase letters, using the host's locale
toLocaleUpperCase()	Returns a string converted to uppercase letters, using the host's locale
toLowerCase()	Returns a string converted to lowercase letters
toString()	Returns a string or a string object as a string
toUpperCase()	Returns a string converted to uppercase letters
trim()	Returns a string with removed whitespaces
trimEnd()	Returns a string with removed whitespaces from the end
trimStart()	Returns a string with removed whitespaces from the start
valueOf()	Returns the primitive value of a string or a string object

 

 

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String Templates까지 함.