JavaScript typeof Operator

When working with JavaScript, it is essential to understand the typeof operator. This operator allows you to determine the data type of a given value or variable. By using the typeof operator, you can easily check whether a value is a string, number, boolean, object, function, or undefined. Let’s explore how the typeof operator works with some examples.

Example 1: Checking the Data Type of a Variable

Let’s say we have a variable called age that stores a person’s age:

let age = 25;
console.log(typeof age); // Output: "number"

In this example, the typeof operator is used to check the data type of the age variable. Since the value stored in age is a number, the output will be “number”.

Example 2: Determining the Data Type of a String

Now, let’s consider a string variable called name:

let name = "John";
console.log(typeof name); // Output: "string"

In this case, the typeof operator is applied to the name variable. As the value stored in name is a string, the output will be “string”.

Example 3: Checking for a Boolean Value

The typeof operator can also be used to determine if a value is a boolean. Let’s take a look at an example:

let isStudent = true;
console.log(typeof isStudent); // Output: "boolean"

In this example, the typeof operator is used to check the data type of the isStudent variable. Since the value stored in isStudent is a boolean, the output will be “boolean”.

Example 4: Identifying an Object

JavaScript objects are complex data types that can store multiple values. Here’s an example of using the typeof operator with an object:

let person = {
  name: "Jane",
  age: 30,
  profession: "Engineer"
};
console.log(typeof person); // Output: "object"

In this case, the typeof operator is applied to the person object. As objects are considered a data type in JavaScript, the output will be “object”.

Example 5: Handling Undefined Values

When a variable is declared but not assigned a value, it is considered undefined. The typeof operator can help identify such cases:

let country;
console.log(typeof country); // Output: "undefined"

In this example, the typeof operator is used to check the data type of the country variable. Since the variable is declared but not assigned a value, the output will be “undefined”.

These examples demonstrate how the typeof operator can be used to determine the data type of different values in JavaScript. By utilizing this operator, you can ensure that your code handles different data types correctly and avoids unexpected errors.

Remember, the typeof operator returns a string representing the data type, such as “number”, “string”, “boolean”, “object”, “function”, or “undefined”. It is a powerful tool for checking and validating data types in JavaScript.