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Write a program to find element occurrence in an array

Input:

const arr = [1, 1, 2, 3, 1, 4];

Output:

// 👉 {1: 3, 2: 1, 3: 1, 4: 1}
Answer 
const arr = [1, 1, 2, 3, 1, 4];
const count = {};


for (const element of arr) {
    if (count[element]) {
        count[element] += 1;
    } else {
        count[element] = 1;
    }
}


console.log(count); // 👉 {1: 3, 2: 1, 3: 1, 4: 1}

The code iterates through the array and uses an object count to keep track of the occurrences of each element. The final output is {1: 3, 2: 1, 3: 1, 4: 1}, indicating how many times each number appears in the array.

Write a program to remove duplicate items from an array

Input:

const arr = [1, 2, 3, 4, 1, 2];

Output:

// 👉 [1, 2, 3, 4]
Answer 
const arr = [1, 2, 3, 4, 1, 2];
const b = [];




const arr = [1, 2, 3, 4, 1, 2];
arr.filter((dup) => {
    if (b.indexOf(dup) === -1) {
        b.push(dup);
    }
});






console.log("removed array value", b); // 👉 [1, 2, 3, 4]

or just do

console.log([...new Set(arr)]) // 👉 [1, 2, 3, 4]

The code iterates through the array and pushes each element into the new array b only if it is not already present in b. This removes duplicate elements and results in [1, 2, 3, 4].

Write a program for the following output using arrow function

Input:

call(2)(4)(6)

Output:

// 👉 48
Answer 
const call = (a) => {
    return (b) => {
        return (c) => {
            return a * b * c
        }
    }
}


//Above can also be written as a one liner


const call = (a) => (b) => (c) => a * b * c;


console.log("output with arrow function", call(2)(4)(6)); // 👉 48

The arrow function syntax achieves the same result as the normal function, where call(2)(4)(6) multiplies the three numbers together, resulting in 48.

Write a program to return resolve if value is less than 7 using Promise

Input:

fun(5)

Output:

// 👉 "number is given 5"
Answer 
function fun(a) {
    let myPromise = new Promise((myResolve, myReject) => {
        if (a < 7) {
            myResolve(`number is given ${a}`);
        } else {
            myReject("Error");
        }
    });


    myPromise.then((result) => {
        console.log(result);
    }).catch((error) => {
        console.log(error);
    });
}


fun(5); // 👉 "number is given 5"

OR this way also possible

const fun = (value) => {
    return new Promise((resolve, reject) => {
        if(value < 5 ){
           resolve('Number less than 5')
        } else {
            reject('Error')
        }
    })
}
    fun(3).then((success) => console.log(success)).catch((second) => console.log(second))

Write a program to multiply two numbers without using the multiply sign in JavaScript

Input:

const a = 5;
const b = 3;

Expected Output:

// 👉 15
Answer 
function multiply(a, b) {
    let answer = a;
    for (let i = 0; i < b - 1; i++) {
        answer += a;
    }
    return answer;
}


console.log(multiply(5, 3));  // 👉 15

Write a program to sort an array in ascending order

Input:

const arr = [3, 2, 5, 4, 1, 0];

Expected Output:

// 👉 [0, 1, 2, 3, 4, 5]
Answer 
const arr = [3, 2, 5, 4, 1, 0];
for (let i = 0; i < arr.length; i++) {
    for (let j = i + 1; j < arr.length; j++) {
        if (arr[i] > arr[j]) {
            let temp = arr[i];
            arr[i] = arr[j];
            arr[j] = temp;
        }
    }
}


console.log("Elements of array sorted in ascending order:", arr);  // 👉 [0, 1, 2, 3, 4, 5]

or

const arr = [3, 2, 5, 4, 1, 0];
const result = arr.sort((a,b) => a - b)
console.log(result)