Join the social network of Tech Nerds, increase skill rank, get work, manage projects...
 
  • What is typeof and how to use it in Javascript

    • 0
    • 0
    • 0
    • 0
    • 0
    • 0
    • 0
    • 0
    • 228
    Comment on it

    In this post, we will discuss about typeof operator in javascript. First we should know what is typeof.

    What is typeof: 

    typeof is an operator that is used to identify the type of any object in javascript. It returns a value that is string. So you can compare any string value from returned value of typeof.

     

    // Examples
    typeof 12;   // number";
    typeof false or typeof true; // "boolean"
    typeof undefined; // "undefined"
    typeof {};     // "object"
    
    // Call with parentheses
    typeof(12);  // "number";

    In the above code, you can see we have used typeof in two ways.

    typeof is an operand and not a function and the second method it is not actually a function call. The operation in parenthesis is evaluated then passed to typeof.

    When to use typeof:
    typeof can be used if you want to check some variable that is undefined or not. If you are using any undefined variable into your code, you can get a ReferenceError. By using typeof into your code can prevent you from this error.

     

    if( typeof foo !== "undefined") {
        // defined
    }else {
        // undefined
    }

    This is how you can use typeof in your code. :)

     

 0 Comment(s)

Sign In
                           OR                           
                           OR                           
Register

Sign up using

                           OR                           
Forgot Password
Fill out the form below and instructions to reset your password will be emailed to you:
Reset Password
Fill out the form below and reset your password: