Every string method in JavaScript

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1. charAt

• String.charAt(index) method takes a parameter index(index position of the string) and
• returns the charter at that index from the string

Examples

const string = "Hello World!";
console.log(string.charAt(4)); // 'o'

2. indexOf

• String.indexOf(searchString) takes a parameter searchString
• and it searches the searchString inside the string starting from the start/left -and returns the index value of the searchString from first occurrence if found, if not returns -1
• if nothing is passed as a parameter, the parameter will be undefined

Examples

const string = 'The code undefined code code'
console.log(string.indexOf('code')) // 4
console.log(string.indexOf('Code')) // -1
console.log(string.indexOf('')) // 0
console.log(string.indexOf()) // 9 // since undefined automatically passed and 'undefined' is in the string and matched it.

3. lastIndexOf

• String.lastIndexOf(searchString) takes a parameter searchString
• and it searches the searchString inside the string starting from the right/end
• and returns the index value of the searchString from last occurrence if found, if not returns -1
• if nothing passed as a parameter, the parameter will be undefined

Examples

const string = "The code undefined code code";
console.log(string.lastIndexOf("code")); // 24
console.log(string.lastIndexOf("Code")); // -1
console.log(string.lastIndexOf("")); // 28
console.log(string.lastIndexOf()); // 9 // since undefined automatically passed and 'undefined' is in the string and matched it.

4. slice

• String.slice() method extracts a section of a string and returns as a new string so they don't change the original string
• syntax
• String.slice(indexStart, indexEnd)
• indexStart is the position from where we want to start taking a slice from the original string
• if negative index is given, slice() will go from the end of the string, end character will index will be -1, second last character index will be -2 and so on
• indexEnd is the position where we want slice() to stop slicing the string
• the indexEnd'th will be excluded
• if indexStart is getter than indexEnd, then slice() will return ''(empty string)

Examples

const string = "The morning is upon us.";
console.log(string.slice(12)); // is upon us.
console.log(string.slice(-11)); // is upon us.
console.log(string.slice(13, 16)); // s u
console.log(string.slice(16, 13)); // ''
console.log(string.slice(-8, -4)); // 'upon'
console.log(string.slice(-8, 4)); // ''
console.log(string.slice(8, -4)); // 'ing is upon'

5. substring

• String.substring() method extracts a section of a string and returns as a new string so they don't change the original string
• syntax
• String.substring(indexStart, indexEnd)
• indexStart is the position from where we want to start taking a slice from the original string
• if negative index is given, substring() assumes any negative index as 0, so extract from the start
• indexEnd is the position where we want substring() to stop slicing the string
• the indexEnd'th will be excluded
• if indexStart is getter than indexEnd, then substring() will swap there positions

Examples

const string = "The morning is upon us.";
console.log(string.substring(12)); // is upon us.
console.log(string.substring(-11)); // is upon us.
console.log(string.substring(13, 16)); // s u
console.log(string.substring(16, 13)); // s u
console.log(string.substring(-8, -4)); // 'upon'
console.log(string.substring(-8, 4)); // 'The'
console.log(string.substring(8, -4)); // 'The morn'

6. split

• String.split(separator) is used whenever we want to divide
• our string into substring based on a separator we pass into the split() method
• and split() method will return those substring ordered inside an array and returns the array
• so it doesn't modify the original array

Examples

const string = "The morning is upon us.";
console.log(string.split()); // [ 'The morning is upon us.' ]
console.log(string.split(" ")); // [ 'The', 'morning', 'is', 'upon', 'us.' ]
console.log(string.split(""));
/* 
[
  'T', 'h', 'e', ' ', 'm',
  'o', 'r', 'n', 'i', 'n',
  'g', ' ', 'i', 's', ' ',
  'u', 'p', 'o', 'n', ' ',
  'u', 's', '.'
]
*/
console.log(string.split("o")); // [ 'The m', 'rning is up', 'n us.' ]

7. includes

• String.includes(searchString) is used whenever we want to see or determine
• if our string is found within another string, if found returns true else false

Examples

const string = "The brown fox jumps over the lazy dog undefined";
console.log(string.includes("fox")); // true
console.log(string.includes("Fox")); // false
console.log(string.includes()); // true

8. startsWith

• String.startsWith(searchString) is used whenever we ant to check if a string starts with another string or not

Examples

const string = "Playing cricket is good for health";
console.log(string.startsWith("Playing")); // true
console.log(string.startsWith("cricket")); // false

9. endsWith

• String.endsWith(searchString) checks whether a string ends with another string or not

Examples

const string = "The cat is beautiful!";
console.log(string.endsWith("beautiful!")); // true
console.log(string.endsWith("beautiful")); // false

10. concat

• String.concat(str1, str2, strN) is used to concatenate strings
• it returns a new string and doesn't modify original strings

Examples

const str1 = "Hello";
const str2 = "World!";
const concatenatedStr = str1.concat(" ", str2); // Hello World!
console.log(concatenatedStr);

/* Performance notes
it is strongly recommended to use assignment operators (+, +=) instead of the concat() method
*/

11. repeat

• String.repeat(count) is used whenever we want to do more copies of a string
• it takes a count parameter which defines the number copies of the string should be done
• returns new string by not modifying original string
• if 0 or no parameter is passed repeat() will return empty string
• if decimal number is passed, repeat() will convert this into an integer
• -1 as counter will return RangeError

Examples

const string = "hello";
const fiveCopies = string.repeat(5); // hellohellohellohellohello
console.log(fiveCopies);

console.log(string.repeat()); // ''
console.log(string.repeat(1)); // hello
console.log(string.repeat(2.5)); // helohelo
console.log(string.repeat(-1)); // RangeError
console.log(string.repeat(1 / 0)); // RangeError

12. trim

• String.trim() is used to remove white space from both start and end of the string
• or removes the leading and trailing white space and line terminator characters from a string.
• it returns new string and does not modify origin string

Examples

const string = " Hello World ";
const trimmedStr = string.trim();

console.log(trimmedStr); // 'Hello World'

13. trimStart

• String.trimStart() is used to remove white space from the start of a string
• or removes the leading white space and line terminator characters from a string.
• it returns new string and does not modify origin string

Examples

const string = " Hello World ";
const trimmedStr = string.trimStart();

console.log(trimmedStr); // 'Hello World '

14. trimEnd

• String.trimEnd() is used to remove white space from the end of a string
• or removes the trailing white space and line terminator characters from a string.
• it returns new string and does not modify origin string

Examples

const string = " Hello World ";
const trimmedStr = string.trimEnd();

console.log(trimmedStr); // ' Hello World'

15. padStart

• String.padStart(targetLength, padString) is used whenever we want to pad our original string
• from the start with another string to reach a given or target length
• if targetLength is given but padString is not given, then padString will be by default space
• it returns new string not modifying original string

Examples

const string = "abc";
console.log(string.padStart(10)); // '       abc'
console.log(string.padStart(10, "foo")); // 'foofoofabc'
console.log(string.padStart(10, "12345678")); // '1234567abc'
console.log(string.padStart(2)); // 'abc'

16. padEnd

• String.padEnd(targetLength, padString) is used whenever we want to pad our original string
• from the end with another string to reach a given or target length
• if targetLength is given but padString is not given, then padString will be by default space
• it returns new string not modifying original string

Examples

const string = "abc";
console.log(string.padEnd(10)); // 'abc       '
console.log(string.padEnd(10, "foo")); // 'abcfoofoof'
console.log(string.padEnd(10, "12345678")); // 'abc1234567'
console.log(string.padEnd(2)); // 'abc'

17. localeCompare

• referenceString.localCompare(compareString) is used whenever we want to compare two strings
• localCompare() returns a numeric value
• if the referenceString occurs before compareString it will return a negative value (-1/-2/-3)
• if the referenceString occurs after compareString it will return a positive value (+1/+2)
• if the referenceString is equivalent to compareString it will return 0

Examples

const a = "a";
const b = "b";

console.log(a.localeCompare(b)); // -1
console.log(b.localeCompare(a)); // 1
console.log(a.localeCompare(a)); // 0

18. search

• String.search(regex) is used to search for a match
• between regular expression and the string object
• search() will always returns an index that is the index of the first match
• search() is case sensitive
• when search fails it returns -1

Examples

const string = "The rain in SPAIN stays mainly in the plain";

console.log(string.search("ain")); // 5 // search() will convert 'ain' into regular expression
console.log(string.search(/ain/)); // 5
console.log(string.search(/AIN/)); // 14
console.log(string.search(/AIN/i)); // 5
console.log(string.search(/w/)); // -1

19. match

• String.match(regex) is used for match
• between regular expression and the string object
• match() will return an array with some information about the match inside
• and it will only return the first match
• when match() fails it returns null

Examples

const string = "The rain in SPAIN stays mainly in the plain";

console.log(string.match("ain")); // match() will convert 'ain' into regular expression
/* 
[
  'ain',
  index: 5,
  input: 'The rain in SPAIN stays mainly in the plain',
  groups: undefined
]
*/
console.log(string.match(/ain/));
console.log(string.match(/AIN/g)); // [ 'AIN' ]
console.log(string.match(/AIN/gi)); // [ 'ain', 'AIN', 'ain', 'ain' ]
console.log(string.match(/w/)); // null

20. matchAll

• String.matchAll(regex) is used for match
• between regular expression and the string object
• matchAll() will return an array with some information about the match inside
• and it will return an iterable of matches containing the results of that search.
• when matchAll() fails it returns empty array []

Examples

const string = "The rain in SPAIN stays mainly in the plain";

console.log([...string.matchAll("ain")]);

// matchAll() will convert this into regular expression like this by adding global modifier
// string.matchAll(/ain/g)
/* 
[
  [
    'ain',
    index: 5,
    input: 'The rain in SPAIN stays mainly in the plain',
    groups: undefined
  ],
  [
    'ain',
    index: 25,
    input: 'The rain in SPAIN stays mainly in the plain',
    groups: undefined
  ],
  [
    'ain',
    index: 40,
    input: 'The rain in SPAIN stays mainly in the plain',
    groups: undefined
  ]
]
*/

console.log([...string.matchAll(/w/gi)]); // []

21. replace

• String.replace(searchString, replaceString) is used whenever we want to
• replace a substring inside our string with another string
• searchString can be string or regular expression
• it returns a new string not modifying original string
• replace only replace the first occurrence of the match
• the second parameter can be a function and the function takes a parameter which is the match
• String.replace(searchString, replaceFunction)

Examples

const string = "Mr Blue has a blue house and a blue car";
console.log(string.replace("blue", "red")); // Mr Blue has a red house and a blue car

const result = string.replace("blue", (match) => {
  return match.toUpperCase();
});
console.log(result); // Mr Blue has a BLUE house and a blue car

console.log(string.replace(/blue/g, "red")); // Mr Blue has a red house and a red car
console.log(string.replace(/blue/gi, "red")); // Mr red has a red house and a red car

22. replaceAll

• String.replaceAll(searchString, replaceString) will replace all the match of the string
• searchString can be string or regular expression
• it returns a new string not modifying original string
• the second parameter can be a function and the function takes a parameter which is the match
• String.replaceAll(searchString, replaceFunction)

Examples

const string = "Mr Blue has a blue house and a blue car";
console.log(string.replaceAll("blue", "red")); // Mr Blue has a red house and a red car

const result = string.replaceAll("blue", (match) => {
  return match.toUpperCase();
});
console.log(result); // Mr Blue has a BLUE house and a BLUE car

console.log(string.replaceAll(/blue/g, "red")); // Mr Blue has a red house and a red car
console.log(string.replaceAll(/blue/gi, "red")); // Mr red has a red house and a red car

23. charCodeAt

• String.codePointAt(index) is UTF-16 based and range is from 0 to 65535
• Returns the Unicode value of the character at the specified location.
• when parameter index is not passed by default it would be 0 index
• if there is no element at the position(index) it'll return NaN

Examples

const str = "Ok 👍";
console.log(str.length); // 5
console.log(str.codePointAt(0)); // 79
console.log(str.codePointAt(1)); // 107
console.log(str.codePointAt(2)); // 32
console.log(str.codePointAt(3)); // 55357
console.log(str.codePointAt(4)); // 56397
console.log(str.codePointAt(5)); // NaN
console.log(str.codePointAt()); // 99

24. codePointAt

• String.codePointAt(index) is Unicode based and range is from 0 to 65535 & > 65355
• Returns the Unicode value of the character at the specified location.
• when parameter index is not passed by default it would be 0 index
• if there is no element at the position(index) it'll return undefined

Examples

const str = "Ok 👍";
console.log(str.length); // 5
console.log(str.code(0)); // 79
console.log(str.codePointAt(1)); // 107
console.log(str.codePointAt(2)); // 32
console.log(str.codePointAt(3)); // 128077
console.log(str.codePointAt(4)); // 56397
console.log(str.codePointAt(5)); // NaN
console.log(str.codePointAt()); // 99

25. fromCharCode

• String.fromCharCode(num) is used whenever we want to get
• actual value from a unicode

Examples

console.log(String.fromCharCode(79)); // 'O'
console.log(String.fromCharCode(107)); // 'k'
console.log(String.fromCharCode(32)); // '  '
console.log(String.fromCharCode(55357)); // �
console.log(String.fromCharCode(56397)); // 'k'

console.log(String.fromCharCode(79, 107, 32, 55357, 56397)); // 'Ok 👍

26. fromCodePoint

• String.fromCodePoint(num) is used whenever we want to get
• actual value from a unicode

Examples

console.log(String.fromCodePoint(79)); // 'O'
console.log(String.fromCodePoint(107)); // 'k'
console.log(String.fromCodePoint(32)); // ' '
console.log(String.fromCodePoint(128077)); // 👍
console.log(String.fromCodePoint(56397)); // �

console.log(String.fromCodePoint(79, 107, 32, 55357, 56397)); // 'Ok 👍'
console.log(String.fromCodePoint(79, 107, 32, 128077)); // 'Ok 👍

27. normalize

• String.normalize(form) // form => NFC/NFD default NFC
• Returns the String value result of normalizing the string into the normalization form named by form as specified in Unicode Standard Annex #15, Unicode Normalization Forms

Examples

// before normalization
let str1 = "\u00c7"; // Ç
console.log(str1.length); // 1

let str2 = "\u0043\u0327"; // ̧C = C + ̧
console.log(str2.length); // 2

// after normalization
str1 = str1.normalize();
console.log(str1.length); // 1
console.log(str1.codePointAt(0)); // 199

str2 = str2.normalize();
console.log(str2.length); // 1
console.log(str2.codePointAt(0)); // 199

str1 = str1.normalize("NFD");
console.log(str1.length);
console.log(str1.codePointAt(0)); // 67
console.log(str1.codePointAt(1)); // 807

28. toLowerCase

• String.toLowerCase() is used whenever we want to all
• the alphabetic character to be lower case or small letter
• toLowerCase() returns a new string without changing the original string

Examples

const string = "My name is Jisan";
console.log(string.toLowerCase()); // my name is jisan

29. toUpperCase

• String.toUpperCase() is used whenever we want to all
• the alphabetic character to be upper case or capital letter
• toUpperCase() returns a new string without changing the original string

Examples

const string = "my name is jisan";
console.log(string.toUpperCase()); // MY NAME IS JISAN

30. toLocaleLowerCase

• String.toLocaleLowerCase(local)
• Converts all alphabetic characters to lowercase, taking into account the host environment's current locale.
• toLocaleLowerCase() returns a new string without changing the original string

Examples

const string = "ISTANBUL";
console.log(string.toLocaleUpperCase("en-US")); // istanbul

console.log(string.toLocaleLowerCase("tr")); // ıstanbul

31. toLocaleUpperCase

• String.toLocaleUpperCase(local)
• Converts all alphabetic characters to uppercase, taking into account the host environment's current locale.
• toLocaleUpperCase() returns a new string without changing the original string

Examples

const string = "istanbul";
console.log(string.toLocaleUpperCase("en-US")); // ISTANBUL

console.log(string.toLocaleUpperCase("tr")); // İSTANBUL

32. toString

• String.prototype.toString()
• Returns a string representation of a string.
• no need to use toString() method explicitly

Examples

const string = "Hello World!";
console.log(string.toString()); // 'Hello World!'

33. valueOf

• String.prototype.valueOf()
• Returns the primitive value of the specified object.
• no need to use valueOf() method explicitly

Examples

const string = "Hello World!";
console.log(string.valueOf()); // 'Hello World!'

34. raw

• String.rawtemplateString

Examples

const string = `C\windows\registration\name\filename.js`;
console.log(string);
/* 
egistration
ame
ilename.js
*/

const escapedFlag = String.raw`C\windows\registration\name\filename.js`;
console.log(escapedFlag); // C\windows\registration\name\filename.js