Type checking using typeof in Javascript - Mini Project: Build & Apply

Type Checking Using typeof in JavaScript

📖 Scenario: Imagine you are building a simple web app that needs to check the type of different values entered by users. This helps the app decide how to handle each value correctly.

🎯 Goal: You will create variables with different types of values, then use typeof to check their types and print the results.

📋 What You'll Learn

Create variables with different types: string, number, boolean, and object

Create a variable to hold the type of one of the values using typeof

Use typeof inside a loop to check types of all variables

Print the type of each variable

💡 Why This Matters

🌍 Real World

Type checking helps programs handle different kinds of data safely, like checking if a user input is a number before doing math.

💼 Career

Understanding data types and how to check them is a basic skill for any JavaScript developer, useful in debugging and writing reliable code.

1

Create variables with different types

Create four variables with these exact names and values: name with value "Alice", age with value 30, isStudent with value true, and details with value { city: "Paris" }.

Javascript

// Create variables name, age, isStudent, and details with the exact values
// Your code here

Need a hint?

Use const to create variables and assign the exact values given.

2

Create a variable to hold the type of name

Create a variable called typeOfName and set it to the type of the variable name using typeof.

Javascript

const name = "Alice";
const age = 30;
const isStudent = true;
const details = { city: "Paris" };

// Create variable typeOfName using typeof on name
// Your code here

Need a hint?

Use typeof name to get the type of name.

3

Check types of all variables using a loop

Create an array called variables containing name, age, isStudent, and details. Then use a for loop with variable value to iterate over variables and create an array called types that stores the type of each value using typeof.

Javascript

const name = "Alice";
const age = 30;
const isStudent = true;
const details = { city: "Paris" };

const typeOfName = typeof name;

// Create array variables with name, age, isStudent, details
// Create empty array types
// Use for loop with value to fill types with typeof value
// Your code here

Need a hint?

Put the variables in an array, then loop over it and use typeof on each item.

4

Print the types of all variables

Use console.log to print the types array.

Javascript

const name = "Alice";
const age = 30;
const isStudent = true;
const details = { city: "Paris" };

const typeOfName = typeof name;

const variables = [name, age, isStudent, details];
const types = [];
for (const value of variables) {
    types.push(typeof value);
}

// Print the types array
// Your code here

Need a hint?

Use console.log(types) to show the array of types.