Here are some of the most fundamental JS string functions.
Assume the code below is declared at the top level in the following examples.
var string = "string"
Changing the case
toLowerCase()
Converts a string to lowercase letters.
let s6 = "STRING".toLowerCase();
console.log(s6); //=> "string"
toUpperCase()
Converts a string to uppercase letters.
let s7 = string.toUpperCase();
console.log(s7); //=> "STRING"
Searching for a substring
indexOf(subst, pos)
It looks for the substr in a string, starting from the given position pos.
console.log(string.indexOf('i')) //=> 3
let string2 = 'string string'
console.log(string2.indexOf('string', 2)) //=> 7
includes()
Checks whether a string contains the specified string/characters.
console.log(string.includes("s")); //=> true
match()
Searches a string for a match against a regular expression, and returns the matches.
const regex = /\w/g;
let s4 = string.match(regex);
console.log(s4); //=> ["s", "t", "r", "i", "n", "g"]
Getting a substring
slice()
Extracts a part of a string and returns a new string.
let s2 = string.slice(0, 3); ///=> str
console.log(s2);
substring()
Extracts a part of a string and returns a new string.
let s2 = string.substring(0, 3); ///=> str
console.log(s2);
Transforming a string
split()
Splits a string into an array of substrings.
let s1 = string.split("");
console.log(s1); //=> ["s", "t", "r", "i", "n", "g"]
concat()
Joins two or more strings, and returns a new joined strings.
let s3 = string.concat("string");
console.log(s3); //=> stringstring
replace()
Searches a string for a specified value, or a regular expression, and returns a new string where the specified values are replaced.
let s5 = string.replace(/s/, "S");
console.log(s5); //=> String
trim()
Removes whitespace from both ends of a string.
let s8 = " strn g ".trim();
console.log(s8); //=> strn g
let s9 = " string ".trimLeft();
console.log(s9); //=> "string "
let s10 = " string ".trimRight();
console.log(s10); //=> " string"
Strings are an important part of any programming language, and JavaScript has many powerful built-in functions that make it easy for developers to use strings. I am also a developer and associate with Masters Dissertation Help UK.