JavaScript String Methods

A developer explains JavaScript string methods, covering properties like length and methods such as charAt, charCodeAt, codePointAt, concat, at, slice, substring, substr, toUpperCase, toLowerCase, isWellFormed, toWellFormed, trim, trimStart, trimEnd, padStart, padEnd, repeat, replace, replaceAll, and split.

A String in JavaScript is a sequence of characters used to store text. js let course = "JavaScript"; Returns the total number of characters in a string. string.length js let company = "OpenAI"; console.log company.length ; 6 Checking password length before registration. Returns the character at a specified index. string.charAt index js let city = "Madurai"; console.log city.charAt 3 ; u M a d u r a i 0 1 2 3 4 5 6 Index 3 contains "u". Returns the Unicode value UTF-16 code of a character. js let letter = "A"; console.log letter.charCodeAt 0 ; 65 console.log "a".charCodeAt 0 ; Output: 97 Returns the Unicode code point of a character. Useful for emojis and special symbols. js let emoji = "😊"; console.log emoji.codePointAt 0 ; 128522 console.log "😊".charCodeAt 0 ; console.log "😊".codePointAt 0 ; codePointAt gives the actual Unicode value. Combines two or more strings. js let firstName = "Annapoorani"; let lastName = " Kadhiravan"; let fullName = firstName.concat lastName ; console.log fullName ; Annapoorani Kadhiravan console.log firstName + lastName ; Returns character at a specific position. Supports negative indexing. js let language = "JavaScript"; console.log language.at 0 ; console.log language.at -1 ; J t Access characters using bracket notation. js let laptop = "Dell"; console.log laptop 0 ; console.log laptop 2 ; D l console.log laptop.charAt 0 ; console.log laptop 0 ; Both return same result. Extracts part of a string. string.slice start,end js let course = "JavaScript"; console.log course.slice 0,4 ; Java console.log course.slice -6 ; Script Extracts characters between indexes. js let company = "Microsoft"; console.log company.substring 0,5 ; Micro js let str = "JavaScript"; console.log str.slice -6 ; console.log str.substring -6 ; Output: Script JavaScript substring doesn't support negative indexes. ⚠️ Deprecated Avoid in new projects Extracts characters based on start position and length. js let city = "Chennai"; console.log city.substr 2,4 ; enna Start at index 2 Take 4 characters Converts string to uppercase. js let name = "annapoorani"; console.log name.toUpperCase ; ANNAPOORANI Converts string to lowercase. js let company = "OPENAI"; console.log company.toLowerCase ; openai Checks whether a string contains valid Unicode characters. js let text = "Hello"; console.log text.isWellFormed ; true Unicode validation before processing text. Converts malformed Unicode into valid Unicode. js let text = "\uD800"; console.log text.toWellFormed ; � Cleaning corrupted text data. Removes spaces from beginning and end. js let email = " user@gmail.com "; console.log email.trim ; user@gmail.com Removes spaces only from beginning. js let text = " Hello"; console.log text.trimStart ; Hello Removes spaces only from end. js let text = "Hello "; console.log text.trimEnd ; Hello Adds characters at the beginning until desired length. js let orderId = "123"; console.log orderId.padStart 6,"0" ; 000123 Generating invoice numbers. Adds characters at the end. js let code = "JS"; console.log code.padEnd 5," " ; JS Repeats a string multiple times. js let star = " "; console.log star.repeat 5 ; Printing separators. Replaces first matching occurrence. js let sentence = "I love Java. Java is powerful."; console.log sentence.replace "Java","JavaScript" ; I love JavaScript. Java is powerful. Only first occurrence is replaced. Replaces all matching occurrences. js let sentence = "Java Java Java"; console.log sentence.replaceAll "Java","JS" ; JS JS JS Converts string into array. js let skills = "HTML,CSS,JavaScript"; let result = skills.split "," ; console.log result ; "HTML", "CSS", "JavaScript" js let sentence = "Learning JavaScript Daily"; console.log sentence.split " " ; "Learning","JavaScript","Daily" | Method | Purpose | |---|---| | length | Count characters | | charAt | Get character | | charCodeAt | Unicode value | | codePointAt | Unicode code point | | concat | Join strings | | at | Access character supports negative index | | | Access character | | slice | Extract part of string | | substring | Extract text no negative index | | substr | Extract by length deprecated | | toUpperCase | Convert to uppercase | | toLowerCase | Convert to lowercase | | isWellFormed | Check valid Unicode | | toWellFormed | Fix invalid Unicode | | trim | Remove spaces both sides | | trimStart | Remove left spaces | | trimEnd | Remove right spaces | | padStart | Add characters at beginning | | padEnd | Add characters at end | | repeat | Repeat string | | replace | Replace first match | | replaceAll | Replace all matches | | split | Convert string to array | References: https://www.w3schools.com/js/js string methods.asp https://www.w3schools.com/js/js string methods.asp