Why understanding the boundary matters in Typescript - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to print numbers from 0 to 4.

Typescript

for(let i = 0; i [1] 5; i++) {
  console.log(i);
}

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

A<=

B<

C>

D>=

Attempts:

3 left

💡 Hint

Common Mistakes

Using <= 5 causes the loop to run one extra time.

We use < because the loop runs while i is less than 5, so it stops before 5.

2fill in blank

medium

Complete the code to check if a number is within the boundary 1 to 10 (inclusive).

Typescript

if(num [1] 1 && num [2] 10) {
  console.log('Inside boundary');
}

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A>=

B<=

C>

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using > 1 excludes 1 from the boundary.

We use >= 1 and <= 10 to include both 1 and 10 in the boundary.

3fill in blank

hard

Fix the error in the loop boundary to avoid an infinite loop.

Typescript

let count = 0;
while(count [1] 5) {
  console.log(count);
  count--;
}

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

A<

B<=

C>=

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using < causes the loop to never end because count decreases.

Using > makes the condition count > 5 false from the start (0 > 5 is false), so the loop does not enter and avoids being infinite. With < or <=, since count is decremented, it moves further away from the exit condition, causing an infinite loop.

4fill in blank

hard

Fill both blanks to create a dictionary of word lengths for words longer than 3 characters.

Typescript

const words = ['apple', 'bat', 'carrot', 'dog'];
const lengths = Object.fromEntries(words.filter(w => w.length > 3).map(word => [[1], [2]]));

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Aword

Bword.length

Cwords.filter(w => w.length > 3)

Dword => word.length

Attempts:

3 left

💡 Hint

Common Mistakes

Using the whole array as a key or value.

We use word as the key and word.length as the value to map each word to its length.

5fill in blank

hard

Fill all three blanks to create an object with uppercase keys and values greater than 0.

Typescript

const data = { a: 1, b: 0, c: 3 };
const result = Object.fromEntries(Object.entries(data).filter(([k,v]) => v > 0).map(([[3],v]) => [[1], [2]]));

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Ak.toUpperCase()

Bv

Ck

DObject.entries

Attempts:

3 left

💡 Hint

Common Mistakes

Using original keys without uppercase.

We use k.toUpperCase() as the new key, v as the value, and k as the variable for keys in the loop.