Array Insertion at End in DSA Javascript - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add a new element at the end of the array.

DSA Javascript

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

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

Apush

Bpop

Cshift

Dunshift

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop instead of push removes the last element.

Using shift or unshift changes the start of the array.

The push method adds an element to the end of the array.

2fill in blank

medium

Complete the code to insert the number 10 at the end of the array.

DSA Javascript

const numbers = [5, 6, 7];
numbers.[1](10);
console.log(numbers);

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

Apop

Bslice

Csplice

Dpush

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop removes elements instead of adding.

Using slice does not modify the original array.

push adds the element 10 at the end of the array numbers.

3fill in blank

hard

Fix the error in the code to correctly add 'apple' at the end of the fruits array.

DSA Javascript

let fruits = ['banana', 'orange'];
fruits.[1]('apple');
console.log(fruits);

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

Apop

Bpush

Cremove

Dadd

Attempts:

3 left

💡 Hint

Common Mistakes

Using non-existent methods like add or remove.

Using pop which removes elements.

The correct method to add an element at the end is push. Methods like remove or add do not exist for arrays.

4fill in blank

hard

Fill both blanks to add 100 at the end of the array and then print the updated array.

DSA Javascript

let data = [10, 20, 30];
data.[1](100);
console.[2](data);

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

Apush

Bpop

Clog

Dprint

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop instead of push removes elements.

Using console.print which is not a JavaScript method.

push adds 100 at the end of data. console.log prints the array.

5fill in blank

hard

Fill all three blanks to add 'end' to the array, store the new length, and print it.

DSA Javascript

let arr = ['start', 'middle'];
let length = arr.[1]('end');
console.[2](length);
console.[3](arr);

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

Apush

Blog

Dpop

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop which removes elements and returns removed item.

Using pop instead of log for printing.

push adds 'end' and returns the new length. console.log prints the length and the updated array.

Practice

1. What does the push() method do when used on a JavaScript array?

easy

A. Adds one or more elements to the end of the array

B. Removes the first element from the array

C. Sorts the array in ascending order

D. Reverses the order of elements in the array

Solution

1. Step 1: Understand the purpose of push()

   The push() method is designed to add elements to the end of an array.

2. Step 2: Compare with other array methods

   Other methods like shift() remove elements, sort() orders elements, and reverse() changes order, but push() only adds at the end.

3. Final Answer:

   Adds one or more elements to the end of the array -> Option A

4. Quick Check:

   push() adds elements at end [OK]

Hint: Remember: push adds at the end, pop removes from end [OK]

Common Mistakes:

• Confusing push() with pop() which removes elements
• Thinking push() adds elements at the start
• Mixing push() with sort() or reverse()

2. Which of the following is the correct syntax to add the element 5 at the end of array arr?

easy

A. arr.add(5);

B. arr.append(5);

C. arr.insertEnd(5);

D. arr.push(5);

Solution

1. Step 1: Recall JavaScript array methods

   JavaScript arrays use push() to add elements at the end.

2. Step 2: Check each option's validity

   add(), insertEnd(), and append() are not valid JavaScript array methods.

3. Final Answer:

   arr.push(5); -> Option D

4. Quick Check:

   Correct syntax for adding at end is push() [OK]

Hint: Use push() to add elements at array end [OK]

Common Mistakes:

• Using non-existent methods like add() or append()
• Confusing push() with unshift() which adds at start
• Missing parentheses in method call

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

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

medium

A. [1, 2, 3]

B. [4, 1, 2, 3]

C. [1, 2, 3, 4]

D. Error

Solution

1. Step 1: Understand initial array and push operation

   The array starts as [1, 2, 3]. The push(4) adds 4 at the end.

2. Step 2: Determine final array content

   After push, the array becomes [1, 2, 3, 4].

3. Final Answer:

   [1, 2, 3, 4] -> Option C

4. Quick Check:

   push(4) adds 4 at end [OK]

Hint: push() adds element at end, so array grows rightwards [OK]

Common Mistakes:

• Thinking push adds element at start
• Expecting original array unchanged
• Confusing push with unshift

4. Identify the error in the following code snippet that tries to add 10 at the end of array nums:

let nums = [1, 2, 3];
nums.push = 10;
console.log(nums);

medium

A. Using assignment instead of calling push as a function

B. Array nums is not defined

C. push method does not exist on arrays

D. Missing semicolon after push

Solution

1. Step 1: Analyze the push usage

   The code assigns 10 to nums.push instead of calling nums.push(10).

2. Step 2: Understand consequences of assignment

   This overwrites the push method with a number, so push no longer works as a function.

3. Final Answer:

   Using assignment instead of calling push as a function -> Option A

4. Quick Check:

   push must be called as a function, not assigned [OK]

Hint: Always call push() with parentheses to add elements [OK]

Common Mistakes:

• Assigning value to push instead of calling it
• Forgetting parentheses after push
• Assuming push is a property, not a method

5. Given the code below, what will be the final state of arr?

let arr = [10];
arr.push(20);
arr.push(30, 40);
arr.push();

hard

A. [10, 20, [30, 40]]

B. [10, 20, 30, 40]

C. [10, 20, 30, 40, undefined]

D. [10, 20, 30]

Solution

1. Step 1: Trace each push call

   Initial array: [10]. arr.push(20) adds 20 -> [10, 20]. arr.push(30, 40) adds both 30 and 40 -> [10, 20, 30, 40]. arr.push() with no arguments adds nothing.

2. Step 2: Confirm final array state

   No undefined or nested arrays are added. Final array is [10, 20, 30, 40].

3. Final Answer:

   [10, 20, 30, 40] -> Option B

4. Quick Check:

   push() adds all args at end; no args means no change [OK]

Hint: push() adds all arguments; no args means no change [OK]

Common Mistakes:

• Thinking push() with no args adds undefined
• Assuming push(30, 40) adds an array instead of separate elements
• Confusing nested arrays with multiple arguments