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Javascript string methods example

lenght, toUpperCase, toLowerCase

const str = "This is JavaScript string";
console.log('Result:', str.length) // Result: 25
console.log('Result:', str.toUpperCase()) // Result:THIS IS JAVASCRIPT STRING
console.log('Result:', str.toLowerCase()) // Result:this is javascript string

includes, startsWith and endsWtih -> boolean(true or false)

Includes, startsWith, endsWtih return booleans value(true or false). Includes used to search words or characters when the search found it to return true.

const str = "This is JavaScript string";
console.log(str.includes('is')); // Result: true
console.log(str.startsWith('This')); // Result: true
console.log(str.endsWith('This')); // Result: false

Search -> postion of item

Search method provides to search index of search team position. If the search found! search method return position of search team otherwise it returns -1 value

const str = "This is JavaScript string";
console.log('is')) // Result: 2
console.log('JavaScript')) // Result: 8
console.log('Script')) // Result: 12
console.log('none')) // Result: -1

match -> array

match method returns an array of words or characters when matches found

Note: don’t confuse with a regular expression (“/is/g“) which was used from the match method.

const str = "This is JavaScript string, JavaScript is great language";
console.log(str.match(/is/g)) // Result: ["is", "is", "is"]
console.log(str.match(/JavaScript/g)) // Result: ["JavaScript", "JavaScript"]
console.log(str.match(/s/g)) // Result: ["s", "s", "s", "s"]

indexOf and lastIndexOf -> index number

IndexOf and lastIndexOf return the number of positions of the index. In the meantime indexOf check left to right which means start to last, but lastIndexOf checks right to left which mean starting from last

const str = "This is JavaScript string";
console.log(str.indexOf('is')) // Result: 2
console.log(str.indexOf('JavaScript')) // Result: 8
console.log(str.indexOf('s')) // Result: 3

console.log(str.lastIndexOf('is')) // Result: 5
console.log(str.lastIndexOf('JavaScript')) // Result: 8
console.log(str.lastIndexOf('s')) // Result: 19

replace, replaceAll -> new string

replace and replaceAll methods replace new words or characters. Replace with the string it will replace the first item when it’s found. But Replace method with regular expression can replace all of the found items.

replaceAll methods replace all of found item

const str = "This is JavaScript string. JavaScript is the great language";
console.log(str.replace('JavaScript', 'JS')) // Result: This is JS string. JavaScript is the great language
console.log(str.replace(/JavaScript/g, 'JS')) // Result: This is JS string. JS is the great language
console.log(str.replaceAll('JavaScript', 'JS')) // Result: This is JS string. JS is the great language

trim => new string

trim methods remove spaces from start and ends. For example; when a user by mistakenly puts space in the input field first and last. trim help to remove these spaces

const str = "      This is JavaScript string      ";
console.log(str) // Result:       This is JavaScript string  
console.log(str.trim()) // Result: This is JavaScript string

charAt => letter

charAt method takes the index and return a letter of the index

const str = "This is JavaScript string";
console.log(str.charAt(8)) // Result: J
console.log(str.charAt(0)) // Result: T

charCodeAt => sky code

Spy code: To understand the charCodeAt method you must need to know about spy code(character against decimal number). Spy code means all of the characters of our keyboard we can see, have decimal number against every character.

Character against decimal

chartCodeAt method take index number as a parameter of character and return spy code decimal number,

const str = "This is JavaScript string";
console.log(str.charCodeAt(5)) // Result: 105
console.log(str.charCodeAt(10)) // Result: 118
console.log(str.charCodeAt(100)) // Result: NaN

fromCharCode => character

Note: To understand fromCharCode, please check the above charCodeAt method where has spy code understanding.

fromCharCode method is the build-in String objects method. which take spy code as a parameter and return characters.

const str = "This is JavaScript string";
console.log(String.fromCharCode(65)) // Result: A
console.log(String.fromCharCode(75)) // Result: M
console.log(String.fromCharCode(36)) // Result: $

concat => new merge string

concat method make multiple string merge/concat into one string

const str = "This is";
const str2 = ' JavaScript string';
const result = str.concat(str2)
console.log('Result: ', result) // Result: This is JavaScript string

split -> array

split make array from string, we can split with can thing, In the example by space and word split is shown

const str = "This is JavaScript string";
console.log(str.split(' ')) // Result: ["This", "is", "JavaScript", "string"]
console.log(str.split('is')) // Result: ["Th", " ", " JavaScript string"]

Slice -> new string with slice

slice takes two parameters as starting point and ending point. when you pass one parameter it’s counts as a starting point and returns a new slice string. If a single parameter is negative it’s counting as ending point

const str = "This is JavaScript string";
console.log(str.slice(8)) // Result: JavaScript string
// slice(startingPoint, endingPoint)
console.log(str.slice(5, 18)) // Result: is JavaScript
console.log(str.slice(2, 23)) // is is JavaScript stri
console.log(str.slice(-8)) // Result: t string

substr -> new string with specific

substr method work similarly slice method. but substr second parameter used as character count. and a first negative value means it will start from the end

  const str = "This is JavaScript string";
  console.log(str.substr(5)) // Result: is JavaScript string
  // substr(startingPoint, counting charecter)
  console.log(str.substr(5, 4)) // Result: is J

  console.log(str.substr(-8, 5)) // Result: t str

substring -> new string specific range

substring method is also similar to the slice method. But substring doesn’t count the last of the second parameter. In my case, its count six-character include space but the parameter was 7

const str = "This is JavaScript string";
console.log(str.substring(1, 7)) // Result: his is
console.log(str.substring(9, 23)) // avaScript stri

repeat -> new string with numer of repeat

const str = "This is JavaScript string";
// Result: This is JavaScript stringThis is JavaScript string

toString -> convert to string

const num = 80;
const str = num.toString();

console.log(typeof num) // Result: number
console.log (typeof str) // Result: string

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