Typescript : Array methods

array_methods.ts

1. // check whether element exists in an array

function checkIndexOf() {
    let emojis:string[] = ['😎️', '🤓️', '🤩️', '😇️']
    console.log(emojis.indexOf('🤩️') !== -1)
}

// output:
true


2. // find last index of an element inside an array

function checkLastIndexOf() {

    let emojis:string[] = [];
    console.log("Last index of 🤩️ before : ", emojis.lastIndexOf('🤩️'))

    emojis = ['😎️', '🤓️', '🤩️', '😇️']
    console.log("Last index of 🤩️ after : ", emojis.lastIndexOf('🤩️'))
}

// output:
Last index of 🤩️ before :  -1
Last index of 🤩️ after :  2


3. // merge two arrays

function mergeArrays() {
    const emojis_1:string[] = ['😎️', '🤓️', '🤩️', '😇️']
    let emojis_2:string[] = ['😡️', '😳️', '👿️', '😍️']
    console.log("result : ", emojis_1.concat(emojis_2))
}

// output:
result :  [ '😎️', '🤓️', '🤩️', '😇️', '😡️', '😳️', '👿️', '😍️' ]


4. // join array elements with specific separator

function joinArraysWithOperator() {
    let emojis:string[] = ['😎️', '🤓️', '🤩️', '😇️']
    console.log("result : ", emojis.join("*"))
}

// output:
result :  😎️*🤓️*🤩️*😇️


5. // push an element to the array

function addElement() {
    let emojis:string[] = ['🤩️', '😇️', '😡️', '😳️']

    // push 😍️ to emojis
    emojis.push('😍️')
    console.log("pushed 😍️ emoji: ", emojis)

    // push 😎️ to emojis
    emojis.push('😎️')
    console.log("pushed 😎️ emoji : ", emojis)
}

// output
pushed 😍️ emoji:  [ '🤩️', '😇️', '😡️', '😳️', '😍️' ]
pushed 😎️ emoji :  [ '🤩️', '😇️', '😡️', '😳️', '😍️', '😎️' ]


6. // removes last element from array

function removeElement() {
    let emojis:string[] = ['🤩️', '😇️', '😡️', '😳️', '😍️', '😎️']

    // pop will remove last emoji(😎️) from emojis
    emojis.pop()
    console.log("popped 😎️ emoji : ", emojis)

    // pop will remove last emoji(😍️) from emojis
    emojis.pop()
    console.log("popped 😍️ emoji: ", emojis)
}

// output
popped 😎️ emoji :  [ '🤩️', '😇️', '😡️', '😳️', '😍️' ]
popped 😍️ emoji:  [ '🤩️', '😇️', '😡️', '😳️' ]


7. // reverse an array

function reverseArray() {
    let emojis:string[] = ['😎️', '🤩️', '🤓️', '😇️'];
    console.log("reverse array : ", emojis.reverse())
}

// output
reverse array :  [ '😇️', '🤓️', '🤩️', '😎️' ]


8. // shift an element in array

function shiftElement() {
    let emojis:string[] = ['😎️', '🤩️', '🤓️', '😇️'];

    const shiftedEmoji = emojis.shift()

    console.log("result array : ", emojis)
    console.log("shifted emoji : ", shiftedEmoji)
}

// output
result array :  [ '🤩️', '🤓️', '😇️' ]
shifted emoji :  😎️


9. // unshift an element to an array

function unShiftElement() {
    let emojis:string[] = ['😡️', '😳️', '👿️', '😍️']
    emojis.unshift('😎️')
    console.log("unshifted 😎️ emoji: ", emojis)
}

// output 
unshifted 😎️ emoji:  [ '😎️', '😡️', '😳️', '👿️', '😍️' ]


10. // get specific section of the array 

function trimArray() {
    let emojis: string[] = [ '😎️', '🤓️', '🤩️', '😇️', '😡️', '😳️', '👿️']
    console.log("result : ", emojis.slice(2, 5))
}

// output
result :  [ '🤩️', '😇️', '😡️' ]


11. // add/replace/remove element from an array
function updateArray() {
    let emojis: string[] = [ '😎️', '🤩️', '😇️', '👿️']

    // add an element to the array
    emojis.splice(4, 0, '😡️')
    console.log("added 😡️ emoji : ", emojis)

    // replace an element to the array
    emojis.splice(1, 1, '🤗️')
    console.log("replaced 🤩️ with 🤗️ emoji : ", emojis)

    // remove one or more elements from an array 
    emojis.splice(2, 2)
    console.log("removed 😇️ and 👿️ emojis : ", emojis)
}


// output
added 😡️ emoji :  [ '😎️', '🤩️', '😇️', '👿️', '😡️' ]
replaced 🤩️ with 🤗️ emoji :  [ '😎️', '🤗️', '😇️', '👿️', '😡️' ]
removed 😇️ and 👿️ emojis :  [ '😎️', '🤗️', '😡️' ]


12. // convert an array to string

function convertToString() {
    let emojis: string[] = [ '😎️', '🤩️', '😇️', '👿️']
    console.log("string from array : ", emojis.toString())
}

// output
string from array :  😎️,🤩️,😇️,👿️


13. // filter an array with specific condition

function filterArray() {
    let emojis_1:string[] = ['😊️', '😍️', '😂️', '😎️', '😇️', '🤩️']
    let emojis_2:string[] = ['👿️', '😎️', '🤓️', '🤓️', '👿️', '😇️', '😎️', '👿️', '🤗️']

    // find common items from two arrays
    let result = emojis_1.filter(f => emojis_2.indexOf(f) !== -1)
    console.log("common emojis between two arrays : ", result);

    // remove duplicate items from an array
    let distinctArr = emojis_2.filter((item, index) => emojis_2.indexOf(item) === index) 

    console.log("duplicate items removed array : ", distinctArr)
}

// output:
common emojis between two arrays :  [ '😎️', '😇️' ]
duplicate items removed array :  [ '👿️', '😎️', '🤓️', '😇️', '🤗️' ]


14. // get new array from given array

function formatArray()  {
    let numbers: Array<number> = [2.6, 1.3, 4.0]
    let result = numbers.map(Math.ceil) // Math.ceil returns smallest max value of given number 

    console.log("result : ", result)
}

// output
result :  [ 3, 2, 4 ]


15. // check if array is satisfying some condition

function isEvenNumber(item) {
    return item % 2 == 0;
}

function checkEvenNumber() {
    let numbers: Array<number> = [2, 4, 6, 8]
    console.log("result : ", numbers.every(isEvenNumber)) // check whether element is even number
}

// output
result :  true


16. // Reduce array from the right

function reduceArrayFromRight() {
    let numbers: Array<number> = [1, 2, 3, 4]
    let result = numbers.reduceRight(function(a, b){ return a + b})

    console.log("result: ", result)
}

// output
result: 10


17. // reduce array from left

function reduceArrayFromLeft() {
    let numbers: Array<number> = [20, 5, 10]
    let result = numbers.reduce(function(a, b){ return a - b})

    console.log("result: ", result)
}

// output
result: 5


18. // check for atleast one condition to be true

function check() {
    let numbers: Array<number> = [1, 3, 8]
    console.log("Atleast one number is even in given array: ", numbers.some(item => item % 2 == 0))
}

// output
Atleast one number is even in given array:  true


19. // sort array

function sortArray() {
    let numbers: Array<number> = [1, 3, 10, 5, 8]
    console.log("sorted array : ", numbers.sort((a, b) => a - b))
}

// output
sorted array :  [ 1, 3, 5, 8, 10 ]


20. // fill array with elements
function fillArray() {
    const emojis = [ '😎️', '😡️', '😇️', '👿️'];

    // fill with 😍️ from position 2 until position 4
    console.log("result 1: ", emojis.fill('😍️', 2, 4));

    // fill with 😇️ from position 1
    console.log("result 2: ", emojis.fill('😇️', 1));

    // fill with 👿️ at all positions
    console.log("result 3: ", emojis.fill('👿️'));
}

// output
result 1:  [ '😎️', '😡️', '😍️', '😍️' ]
result 2:  [ '😎️', '😇️', '😇️', '😇️' ]
result 3:  [ '👿️', '👿️', '👿️', '👿️' ]