How assignment compatibility is checked in Typescript - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a variable with type number.

Typescript

let age: [1] = 30;

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

Anumber

Bstring

Cboolean

Dany

Attempts:

3 left

💡 Hint

Common Mistakes

Using string type when assigning a number.

Using boolean type for numeric values.

The variable age is declared with type number, so it can only hold numeric values.

2fill in blank

medium

Complete the code to assign a string value to a variable declared as string.

Typescript

let name: string = [1];

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

A25

B"Alice"

Ctrue

Dnull

Attempts:

3 left

💡 Hint

Common Mistakes

Assigning a number or boolean to a string variable.

Forgetting to use quotes around text.

The value assigned to name must be a string, so it needs to be in quotes like "Alice".

3fill in blank

hard

Fix the error by completing the code to assign a compatible type.

Typescript

let isActive: boolean = [1];

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

Afalse

Bnull

C1

D"true"

Attempts:

3 left

💡 Hint

Common Mistakes

Using string "true" instead of boolean true.

Using numbers like 1 or 0 for boolean.

The variable isActive expects a boolean value. Only false is a valid boolean here.

4fill in blank

hard

Fill both blanks to create a compatible assignment between two interfaces.

Typescript

interface Person { name: string; age: number; }
interface Employee extends Person { [1]: string; }
let emp: Employee = { name: "Bob", age: 25, [2]: "Manager" };

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

Aposition

Bsalary

Ddepartment

Attempts:

3 left

💡 Hint

Common Mistakes

Using different property names in interface and object.

Using a property not declared in the interface.

The Employee interface adds a position property. The object emp must include this property with a string value.

5fill in blank

hard

Fill all three blanks to complete a function that checks assignment compatibility with union types.

Typescript

function printId(id: [1]) {
  if (typeof id === [2]) {
    console.log("ID is a number: " + id);
  } else if (typeof id === [3]) {
    console.log("ID is a string: " + id);
  }
}

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

Anumber | string

B"number"

C"string"

Dboolean

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect type strings in typeof checks.

Not matching the union type in the function parameter.

The function accepts an id that can be a number or string. The typeof checks must match the string literals "number" and "string".