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• toLowerCase / toUpperCase()\

const str = "Hello";
const low = str.toLowerCase(); // hello
const up = str.toUpperCase(); // HELLO

• concat(...items)
  Combines two or more strings and returns one string

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

• split(separator, limit)
  Splits a string into an array by the specified separator, which can be a substring or a regular expression

const str = "Just some text";
const arr = str.split(" ");
arr = ["Just", "some", "text"];

• repeat(count)
  Repeats the string the specified number of times

const str = "hey";
const newStr = str.repeat(3);
// newStr = "heyheyhey"

• charAt(index)
  Returns a character at the specified index

const str = "hello";
const char = str.charAt(1);
// char = "e"

• includes(substr, startPositon)
  Checks if the string contains the specified substring and returns true/false

const str = "[email protected]";
str.includes("gmail"); // true

• indexOf / lastIndexOf(substr, startPositon)
  Returns the index of the first/last substring found, otherwise returns -1

const str = "[email protected]";
str.indexOf("@"); // 6
str.lastIndexOf("m"); // 15

• endsWith / startsWith(substr, searchLength)
  Checks if the string ends/starts with the specified substring and returns true/false

const link = "www.google.com";
link.startsWith("www"); // true
link.endsWith(".com"); // true

• search(substr)
  Checks if there is a specified substring or regular expression in the string and returns the index of the beginning of the match

const str = "first name, second name";
str.search("name"); // 6

• slice(start, end)
  Extracts part of the string starting at the start position and ending at the end-1 position

const str = "javascript";
const substr = str.slice(4); // script
const substr = str.slice(0, 4); // java

• substring(start, end)
  Extracts substring from a string between start and end. Unlike slice(), you can set start more than end.

const str = "javascript";
const substr = str.substring(4); // script
const substr2 = str.substring(4, 0); // script

• substr(start, length)
  Extracts part of a string of a specified length. The first parameter can be negative, then the position is determined from the end of the string.

const str = "typescript";
const sub = str.substr(4, 6); // script
const sub2 = str.substr(-6); // script

• replace(substr, newSubstr)
  Searches for the specified substring (or regular expression) in the string and replaces it with another one

const str = "typescript";
const str2 = str.replace("type", "java");
// str2 = javascript

• replaceAll(substr, newSubstr)
  Replaces all found matches with another string or passed function

const str = "one two three";
const str2 = str.replaceAll(" ", "-");
// str2 = one-two-three

• padStart / padEnd(strLength, str)
  Adds padding at the beginning/end of a string until the string reaches the length specified by the first parameter

const msg = "hello";
msg.padStart(10, "_"); // "_____hello"
msg.padStart(7); // "  hello"
msg.padEnd(10, "*"); // "hello*****"

• trim / trimStart / trimEnd()
  Deletr spaces at both ends of the string, either only at the beginning or only at the end

const str = "  hello   ";
str.trim(); // "hello"
str.trimStart(); // "hello   "
str.trimEnd(); // "  hello"

• charCodeAt(index)
  Returns the ASCII code of the character at the specified index

const str = "AaBbCc";
str.charCodeAt(); // 65 (because it's "A")
str.charCodeAt(3); // 98 (because it's "b")

• fromCharCode(...code)
  Converts ASCII code to readable characters

const str = String.fromCharCode(74, 83);
// str = "JS"