JavaScript Basic String Functions

k_penguin_sato profile image K-Sato ・2 min read

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


Converts a string to lowercase letters.

let s6 = "STRING".toLowerCase();
console.log(s6); //=> "string"


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


Checks whether a string contains the specified string/characters.

console.log(string.includes("s")); //=> true


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


Extracts a part of a string and returns a new string.

let s2 = string.slice(0, 3); ///=> str


Extracts a part of a string and returns a new string.

let s2 = string.substring(0, 3); ///=> str

Transforming a string


Splits a string into an array of substrings.

let s1 = string.split("");
console.log(s1); //=> ["s", "t", "r", "i", "n", "g"]


Joins two or more strings, and returns a new joined strings.

let s3 = string.concat("string");
console.log(s3); //=> stringstring


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


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"


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As a programmer from essay writers in cheap with the help of string functions you can control much of behavior of website from fonts to even text or even background colors Good practicing example but it would be much better to demonstrate these functions in some handy real world project.


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.