Array Deletion at Beginning in DSA Javascript - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to remove the first element from the array.

DSA Javascript

let arr = [1, 2, 3, 4];
arr.[1]();
console.log(arr);

Drag options to blanks, or click blank then click option'

Apop

Bshift

Cslice

Dpush

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop() removes the last element, not the first.

Using push() adds elements instead of removing.

The shift() method removes the first element from an array.

2fill in blank

medium

Complete the code to remove the first element and store it in a variable.

DSA Javascript

let arr = ['a', 'b', 'c'];
let first = arr.[1]();
console.log(first);

Drag options to blanks, or click blank then click option'

Apop

Bsplice

Cslice

Dshift

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop() returns the last element, not the first.

Using slice() does not modify the original array.

shift() removes and returns the first element of the array.

3fill in blank

hard

Fix the error in the code to correctly remove the first element.

DSA Javascript

let numbers = [10, 20, 30];
numbers.[1](0, 1);
console.log(numbers);

Drag options to blanks, or click blank then click option'

Apop

Bshift

Csplice

Dslice

Attempts:

3 left

💡 Hint

Common Mistakes

Using slice() expecting it to remove elements modifies nothing.

Using pop() removes the last element, not the first.

splice(0, 1) removes one element starting at index 0, effectively removing the first element.

4fill in blank

hard

Fill both blanks to remove the first element and print the updated array.

DSA Javascript

let fruits = ['apple', 'banana', 'cherry'];
fruits.[1]();
console.[2](fruits);

Drag options to blanks, or click blank then click option'

Ashift

Bpop

Clog

Dprint

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop() removes the last element, not the first.

Using console.print() is not a valid JavaScript method.

shift() removes the first element; console.log() prints the array.

5fill in blank

hard

Fill all three blanks to remove the first element, store it, and print both values.

DSA Javascript

let colors = ['red', 'green', 'blue'];
let removed = colors.[1]();
console.[2](removed);
console.[3](colors);

Drag options to blanks, or click blank then click option'

Ashift

Blog

Dpop

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop() removes the last element, not the first.

Using console.print() instead of console.log().

shift() removes and returns the first element; console.log() prints values.

Practice

1. What does the shift() method do to an array in JavaScript?

easy

A. Adds an element at the end

B. Removes the last element and returns it

C. Adds an element at the beginning

D. Removes the first element and returns it

Solution

1. Step 1: Understand the shift() method

   The shift() method removes the first element from an array and returns that element.

2. Step 2: Compare with other array methods

   pop() removes the last element, unshift() adds at the beginning, and push() adds at the end.

3. Final Answer:

   Removes the first element and returns it -> Option D

4. Quick Check:

   shift() removes first element [OK]

Hint: Remember: shift = remove from start [OK]

Common Mistakes:

• Confusing shift() with pop()
• Thinking shift() adds elements
• Mixing shift() with unshift()

2. Which of the following is the correct syntax to remove the first element from an array arr in JavaScript?

easy

A. arr.shift()

B. arr.delete(0)

C. arr.unshift()

D. arr.pop()

Solution

1. Step 1: Identify the method to remove first element

   The method to remove the first element is shift().

2. Step 2: Check other options

   pop() removes last element, unshift() adds elements at start, and delete is not a valid array method.

3. Final Answer:

   arr.shift() -> Option A

4. Quick Check:

   Use shift() to remove first element [OK]

Hint: Use arr.shift() to remove first element [OK]

Common Mistakes:

• Using pop() instead of shift()
• Trying to use delete() on arrays
• Confusing unshift() with shift()

3. What will be the output of the following code?

let arr = [10, 20, 30, 40];
let removed = arr.shift();
console.log(arr);
console.log(removed);

medium

A. [20, 30, 40] and 10

B. [10, 20, 30] and 40

C. [20, 30, 40] and 40

D. [10, 20, 30] and 10

Solution

1. Step 1: Apply shift() on the array

   shift() removes the first element (10) from arr and returns it.

2. Step 2: Check the updated array and removed value

   After removal, arr becomes [20, 30, 40], and removed stores 10.

3. Final Answer:

   [20, 30, 40] and 10 -> Option A

4. Quick Check:

   shift() removes first element 10 [OK]

Hint: shift() returns removed first element [OK]

Common Mistakes:

• Expecting last element removed
• Confusing returned value with array
• Not updating array after shift()

4. Find the error in the following code that tries to remove the first element from array nums:

let nums = [5, 10, 15];
nums.remove(0);
console.log(nums);

medium

A. remove() removes last element, not first

B. remove() is not a valid array method

C. remove() requires two arguments

D. Code is correct and works fine

Solution

1. Step 1: Check the method used

   The method remove() does not exist for JavaScript arrays.

2. Step 2: Identify correct method to remove first element

   To remove the first element, use shift() instead of remove().

3. Final Answer:

   remove() is not a valid array method -> Option B

4. Quick Check:

   Use shift() to remove first element, not remove() [OK]

Hint: Use shift(), not remove(), to delete first element [OK]

Common Mistakes:

• Using remove() instead of shift()
• Assuming remove() exists in JS arrays
• Not checking method names carefully

5. Given an array data = [1, 2, 3, 4, 5], you want to remove the first two elements efficiently. Which code snippet correctly achieves this?

hard

A. data.shift(2);

B. data.pop(); data.pop();

C. data.splice(0, 2);

D. data.slice(2);

Solution

1. Step 1: Understand each method's effect

   shift(2) is invalid; shift() removes one element from start and takes no arguments. splice(0, 2) removes two elements starting at index 0 in one call. pop() removes from end, not start. slice(2) returns a new array without first two elements but does not modify original.

2. Step 2: Choose the best method to remove first two elements

   splice(0, 2) removes first two elements efficiently and modifies the original array.

3. Final Answer:

   data.splice(0, 2); -> Option C

4. Quick Check:

   splice(0, 2) removes first two elements [OK]

Hint: Use splice(0, 2) to remove first two elements at once [OK]

Common Mistakes:

• Using pop() which removes from end
• Using slice() which does not modify original array
• Using shift(2) which is invalid