arrays.md

Arrays

1. What will be the output?

   let array = [1, 2, 3, 4, 5, 6];
   let [a, b, , ...rest] = array;
   
   console.log(a)
   console.log(b)
   console.log(c)
   console.log(rest)
   let c;

   • A: 1, 2, 3, [ 4, 5, 6 ]
   • B: 1, 2, c is not defined
   • C: 1, 2, NaN, undefined
   • D: 1, 2, c is not defined, [4, 5, 6]
   
   
   Answer

   Option: B

---

2. What will be the output?

   let array1 = [1, 2, 3, 4, 5, 6];
   let array2 = array1
   array2.push(7, 8, 9, 10)
   console.log(array1)
   console.log(array2.sort())

   • A: [ 1, 2, 3, 4, 5, 6 ], [ 1, 10, 2, 3, 4, 5, 6, 7, 7, 8, 8, 9, 9 ]
   • B: [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ], [ 1, 10, 2, 3, 4, 5, 6, 7, 8, 9 ]
   • C: [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 7, 8, 9, 10 ], [ 1, 2, 3, 4, 5, 6, 7, 7, 8, 8, 9, 9, 10 ]
   • D: [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 7, 8, 9, 10 ], [ 1, 2, 3, 4, 5, 6 ]
   
   
   Answer

   Option: B

---

3. What will be the output?

   let array = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
   function checkNum(num) {
       return num >= 4;
   }
   
   let newArray1 = [array.map((item) => {
       return item
   })].filter(checkNum)
   
   let newArray2 = array.filter(checkNum).map((item) => {
       return item
   })
   
   console.log(newArray1)
   console.log(newArray2)

   • A: [ [] ], [ [ 4, 5, 6, 7, 8, 9, 10 ] ]
   • B: NaN, []
   • C: [], [ 4, 5, 6, 7, 8, 9, 10 ]
   • D: [ [] ], [ 5, 6, 7, 8, 9, 10 ]
   
   
   Answer

   Option: C

---

4. Guess the output

    let array = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
   function checkNum(num) {
       return num > 4;
   }
   let newArray = [array.filter(checkNum).map((item, index) => {
       return item - array[index]
   }).reduce((acc, curr) => {
       return acc + curr
   })]
   
   console.log(newArray)

   • A: [ 24 ]
   • B: 24
   • C: NaN
   • D: Undefined
   
   
   Answer

   Option: A

---

5. Guess the following output?

   const doSomething = (a, b) => {
       return [a + b, a - b, a * b, a / b]
   }
   let [...rest] = doSomething(4, 2)
   
   console.log(rest * rest)

   • A: [ 36, 4, 64, 4 ]
   • B: 18
   • C: NaN
   • D: rest is not defined
   
   
   Answer

   Option: C

---

6. Guess the following output?

   const doSomething = (a, b) => {
       return [a + b, a - b, a * b, a / b]
   }
   let someVariable = 5;
   let [...rest] = doSomething(4, 2)
   
   someVariable = rest.reduce((acc, total) => {
     return 0 + total;
   });
   
   console.log(someVariable)

   • A: 960
   • B: 192
   • C: NaN
   • D: 2
   
   
   Answer

   Option: D

---

7. Guess the following output?

   const doSomething = (a, b) => {
       return [a + b, a - b, a * b, a / b]
   }
   let someVariable = 5;
   let [...rest] = doSomething(4, 2)
   
   someVariable = rest.reduce((acc = 1, total) => {
     return acc + total;
   });
   
   console.log(someVariable)

   • A: 19
   • B: 192
   • C: NaN
   • D: 18
   
   
   Answer

   Option: A

---

8. Guess the following output?

   const nums = [1, 2, 3, 4, 5, 6];
   
   const res = nums.forEach((item) => {
     return item * item;
   });
   
   console.log(res);

   • A: null
   • B: [ 1, 4, 9, 16, 25, 36 ]
   • C: [1, 2, 3, 4, 5, 6]
   • D: Undefined
   
   
   Answer

   Option: D

---

9. Guess the following output?

   let array = [1, 2, 3];
   let array2 = array;
   let array3 = [...array];
   
   console.log(array.concat(4));
   console.log(array2.concat(5));
   console.log(array3.concat(6, 7));

   • A: [ 1, 2, 3, 4 ], [ 1, 2, 3, 5 ], [ 1, 2, 3, 6, 7 ]
   • B: [ 1, 2, 3, 4, 5 ], [ 1, 2, 3, 4, 5 ], [ 1, 2, 3, 6, 7 ]
   • C: [ 1, 2, 3 ], [ 1, 2, 3, 4, 5 ], [ 1, 2, 3, 6, 7 ]
   • D: [ 1, 2, 3, 4 ], [ 1, 2, 3, 5 ], [ 1, 2, 3, 6, 7 ]
   
   
   Answer

   Option: A

---

10. Guess the following output?

    const clothes = ['jacket', 't-shirt'];
    clothes.length = 0;
    
    console.log(clothes[0]);

    • A: jacket
    • B: undefined
    • C: error
    • D: not defined
    
    
    Answer

    Option: B