Array Insertion at End in DSA Typescript - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

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

DSA Typescript

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

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

Apush

Bshift

Cpop

Dunshift

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop instead of push removes the last element.

Using shift or unshift affects 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 Typescript

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

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

Ashift

Bpop

Cunshift

Dpush

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop removes elements instead of adding.

Using unshift adds elements at the start, not the end.

The push method appends the element 10 to the end of the array.

3fill in blank

hard

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

DSA Typescript

let greetings = ['hi', 'hey'];
greetings.[1]('hello');
console.log(greetings);

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

Apush

Bunshift

Cshift

Dpop

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop removes the last element instead of adding.

Using shift removes the first element.

Using push adds 'hello' at the end of the array.

4fill in blank

hard

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

DSA Typescript

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

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

Apush

Bpop

Clength

Dshift

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop removes elements instead of adding.

Using shift removes from the start.

Trying to call length as a method instead of property.

push adds 100 at the end, and length gives the array size.

5fill in blank

hard

Fill the blanks to add 'end' at the end, then remove the first element, and finally print the updated array.

DSA Typescript

let arr = ['start', 'middle'];
arr.[1]('end');
arr.[2]();
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 shift removes the last element.

Using unshift adds at the start instead of removing.

push adds 'end' at the end, shift removes the first element, and then printing arr shows the updated array.

Practice

1. What does inserting an element at the end of an array do?

easy

A. Adds the element as the last item in the array

B. Removes the first element of the array

C. Replaces the first element with the new element

D. Sorts the array in ascending order

Solution

1. Step 1: Understand array insertion

   Inserting at the end means adding a new element after the last existing element.

2. Step 2: Effect on array

   The new element becomes the last item, increasing the array size by one.

3. Final Answer:

   Adds the element as the last item in the array -> Option A

4. Quick Check:

   Insertion at end = append last [OK]

Hint: Insertion at end means append after last element [OK]

Common Mistakes:

• Confusing insertion at end with removal
• Thinking insertion replaces elements
• Assuming insertion sorts the array

2. Which of the following is the correct TypeScript syntax to insert an element `5` at the end of array `arr`?

easy

A. arr.insert(5);

B. arr.add(5);

C. arr.push(5);

D. arr.append(5);

Solution

1. Step 1: Identify correct method for insertion at end

   In TypeScript (JavaScript), the method to add at the end is `push()`.

2. Step 2: Check other options

   Methods `add()`, `insert()`, and `append()` do not exist on arrays in TypeScript.

3. Final Answer:

   arr.push(5); -> Option C

4. Quick Check:

   Use push() to add at end [OK]

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

Common Mistakes:

• Using non-existent methods like add or append
• Confusing push() with pop()
• Trying to assign directly to arr[arr.length]

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

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

medium

A. [4, 1, 2, 3]

B. [1, 2, 3, 4]

C. [1, 2, 3]

D. [1, 2, 4, 3]

Solution

1. Step 1: Initial array state

   Array starts as [1, 2, 3].

2. Step 2: Apply push(4)

   push(4) adds 4 at the end, so array becomes [1, 2, 3, 4].

3. Final Answer:

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

4. Quick Check:

   push adds element at end [OK]

Hint: push() adds element at array end [OK]

Common Mistakes:

• Thinking push adds at start
• Confusing push with unshift
• Expecting array to remain unchanged

4. Identify the error in the following TypeScript code that tries to insert `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 method

B. Array nums is not declared properly

C. push method does not exist on arrays

D. Console.log syntax is incorrect

Solution

1. Step 1: Analyze push usage

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

2. Step 2: Effect of assignment

   This overwrites the push method, so no insertion happens and push is lost.

3. Final Answer:

   Using assignment instead of calling push method -> Option A

4. Quick Check:

   push must be called as a function [OK]

Hint: Call push() as a function, don't assign to it [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 an empty array `let data: number[] = [];`, which code snippet correctly inserts numbers 1 to 3 at the end of the array using a loop?

hard

A. for(let i = 0; i < 3; i++) { data.push(i); }

B. for(let i = 1; i <= 3; i++) { data[i] = i; }

C. for(let i = 1; i < 3; i++) { data.push(i); }

D. for(let i = 1; i <= 3; i++) { data.push(i); }

Solution

1. Step 1: Understand loop range and insertion

   We want to insert 1, 2, 3 at the end, so loop from 1 to 3 inclusive.

2. Step 2: Check each option

   A pushes 0,1,2 instead of 1,2,3.
   B assigns directly to indices 1,2,3 leaving index 0 empty.
   C uses push with i from 1 to 3, correctly adding 1,2,3.
   D loops from 1 to 2 only, missing 3.

3. Final Answer:

   for(let i = 1; i <= 3; i++) { data.push(i); } -> Option D

4. Quick Check:

   Loop 1 to 3 with push() adds correct elements [OK]

Hint: Loop from 1 to 3 and push each value [OK]

Common Mistakes:

• Using wrong loop range
• Assigning to array indices instead of push
• Starting loop at 0 instead of 1