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K-Sato
K-Sato

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JavaScript Basic String Functions

#javascript

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"
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Changing the case

toLowerCase()

Converts a string to lowercase letters.

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

Converts a string to uppercase letters.

let s7 = string.toUpperCase();
console.log(s7); //=> "STRING"
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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
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includes()

Checks whether a string contains the specified string/characters.

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

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

let s2 = string.substring(0, 3); ///=> str
console.log(s2);
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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"]
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concat()

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

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

Oldest comments (33)

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aliciab13550469 profile image
Alicia Black •

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.

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amelia112 profile image
Amelia •

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harrywilliams1 •

String functions are used in computer programming languages to manipulate strings or query information about strings (some functions will be executed at the same time). Most programming languages with string data types will have some string functions. Source: professional assignment writing UK by British Essay Writers.

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elmadavis profile image
elmadavis •

Is there any replace function used in Java? These mentioned methods or functions are useful. I need assignment writing help from any developer here I need to use these functions. Can we use them with individual data types like int, var, char rather than a string?

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Myprivate Mentor • • Edited

I was just tasked to replace function using java while seeking for assignment writing help . Thanks for this information as it is really very helpful.

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kittydurgans •

This is needed! slope unblocked

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Jasmine • • Edited

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