Let's understand javascript String functions and how to use them.

String.charAt()

Returns a string representing the character at the given index.

const str = "Hello World";
str.charAt(0); // "H"

String.charCodeAt()

Returns a number representing the UTF-16 code unit value of the character at the given index.

const str = "Hello World";
str.charCodeAt(0); // 72

String.concat()

Returns a new string containing the concatenation of the given strings.

const str = "Hello";
const str2 = " World";
str.concat(str2); // "Hello World"

console.log(`${str}${str2}`); // "Hello World"
console.log(str + str2); // "Hello World"

String.endsWith()

Returns true if the string ends with the given string, otherwise false.

const str = "Hello World";
str.endsWith("World"); // true

String.includes()

Returns true if the string contains the given string, otherwise false.

const str = "Hello World";
str.includes("World"); // true

String.indexOf()

Returns the index within the string of the first occurrence of the specified value, or -1 if not found.

const str = "Hello World";
str.indexOf("World"); // 6

String.lastIndexOf()

Returns the index within the string of the last occurrence of the specified value, or -1 if not found.

const str = "Hello World";
str.lastIndexOf("World"); // 6

String.match()

Returns a list of matches of a regular expression against a string.

const str = "Hello World";
str.match(/[A-Z]/); // ["H"]

String.matchAll()

Returns a list of matches of a regular expression against a string.

const str = "Hello World";
str.matchAll(/[A-Z]/g); // ["H", "W"]

// OR
str.match(/[A-Z]/g); // ["H", "W"]

String.padEnd()

Returns a new string with some content padded to the end of the string.

const str = "Hello";
str.padEnd(15, "World"); // "HelloWorldWorld"

String.padStart()

Returns a new string with some content padded to the start of the string.

const str = "Hello";
str.padStart(15, "World"); // "WorldWorldWorldHello"

String.repeat()

Returns a new string which contains the specified number of copies of the string.

const str = "Hello";
str.repeat(3); // "HelloHelloHello"

String.replace()

Returns a new string with some or all matches of a regular expression replaced by a replacement string.

const str = "Hello World";
str.replace("l", "*"); // "He*lo World"

String.replaceAll()

Returns a new string with some or all matches of a regular expression replaced by a replacement string.

const str = "Hello World";
str.replaceAll("l", "*"); // "He**o Wor*d"

OR;
str.replace(/l/g, "*"); // "He**o Wor*d"

String.search()

Returns the index within the string of the first occurrence of the specified value, or -1 if not found.

const str = "Hello World 1";
const regex = /[^\D\s]/g; // Find digit
str.search(regex); // 12

String.slice()

Returns a new string containing the characters of the string from the given index to the end of the string.

const str = "Hello World";
str.slice(6); // "World"

String.split()

Returns an array of strings split at the given index.

const str = "Hello World";
str.split(" "); // ["Hello", "World"]

String.startsWith()

Returns true if the string starts with the given string, otherwise false.

const str = "Hello World";
str.startsWith("Hello"); // true

String.substring()

Returns a new string containing the characters of the string from the given index to the end of the string.

const str = "Hello World";
str.substring(1, 2); // "e"

NOTE: substring takes parameters as (from, to).

String.substr()

Returns a new string containing the characters of the string from the given index to the end of the string.

const str = "Hello World";
str.substr(1, 2); // "el"

NOTE: substr takes parameters as (from, length).

String.toLowerCase()

Returns a new string with all the uppercase characters converted to lowercase.

const str = "Hello World";
str.toLowerCase(); // "hello world"

String.toUpperCase()

Returns a new string with all the lowercase characters converted to uppercase.

const str = "Hello World";
str.toUpperCase(); // "HELLO WORLD"

String.toString()

Returns the string representation of the specified object.

const str = new String("Hello World");
console.log(str); // Object of String
str.toString(); // "Hello World"

String.trim()

Returns a new string with the leading and trailing whitespace removed.

const str = "  Hello World  ";
str.trim(); // "Hello World"

String.trimEnd()

Returns a new string with the trailing whitespace removed.

const str = "  Hello World  ";
str.trimEnd(); // "  Hello World"

String.trimStart()

Returns a new string with the leading whitespace removed.

const str = "  Hello World  ";
str.trimStart(); // "Hello World  "

Thank you for reading 😊

Got any questions or additional? please leave a comment.

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Rahul SharmaFollow

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