string

str="mynewstr123"

Indexing, includes and slicing strings is the same as array. Other similar methods

• indexOf, lastIndexOf → get the index of a character
  • the index of can be more than one character and it will give the index of the first character matching that word
  • same with starting index`

Split string into an array

str.split("t", limit) // array ["mynews", "r123"]

• can limit the length of the array

Search for start and ends with

str.startsWith("my", position) // true
str.endsWith("R123") // false, it's case sensitive

• the position check whether the string start with that substring at a given position

Repeat a string some times, similar to Python *

"123".repeat(3) // "123123123"

• count must be a valid integer >= 0

Manipulate casing

"stR".toLowerCase() // str
"stR".toUpperCase() // STR
"stR"[0].toUpperCase() + "stR".slice(1) // StR

Remove white spaces

" my str ".trimStart() // "my str " 
" my str ".trim() // "my str"
" my str ".trimeEnd() // " my str"

Add whitespace padding to string to reach some length

"mystr".padStart(10)
'     mystr'
"mystr".padEnd(10,"pad")
'mystrpadpa'

• the pad will repeat the pad string until that length

Replace strings

"mystr123123".replace(123, 456) // mystr456123
str.replace(123,match => "**"+match+"**" ) // 'mynewstr**123**123'
"mystr123123".replaceAll(123, 456) // mystr456456

• create a new string object of replaced
• replace without replace all will only replace the first occurence
• it can also take a function for replacing

Search the string with regular expression

str.search(/\d+/) // Number: index

• use // to enclose regexp
• returns the index where the first found, or -1

Match string using regular expression

str.match(/123/g) // Array ['123', '123']
[...str.matchAll(/123/g)] // Array [ [match, index, input] , [] ]

• return a list of matches or details about the match in an array