Uncaught TypeError: Cannot read property of undefined

Out of the six primitive types defined in JavaScript, namely boolean, string, symbol, number, Null, and undefined, no other type throws as many errors as Undefined.

The error most often than not is faced when the scripts come across uninitialized variable or object.

Description

‘Undefined’ is the property of the global object. If you don’t assign any value to a variable is of type ‘undefined’. A code also return the undefined value when the evaluated variable doesn’t have any assigned value.

Code structure

function test(t) {      //defining a function
if (t === undefined) { //if t=undefined, call tt
console.log(t.tt) //call tt member from t
}
return t;
}var a; //a is a variable with undefined valueconsole.log(test(a)); //function call

Error

When you run this code, you’ll get:

Image for post

Debugging

If you get undefined error, you need to make sure that which ever variables throws undefined error, is assigned a value to it.

function test(t) {      //defining a function
if (t === undefined) { //if t=undefined, call tt
console.log(t) //call t
}
return t;
}var a=10; //a is a variable with undefined valueconsole.log(test(a)); //function call

Output

Image for post

Catch Before It Happens.

Image for post

Ability to work with uninitiated variables/objects is one of the plus points of JavaScript over other languages like Java, C etc. So many times developers are tempted to use this feature, even though it not a very good practice. So if you are a developer that is addicted to not initializing the variables, you can at least attempt to catch the problems before they happen through simple statement.

if (typeof(jsvariable) == 'undefined') {
...
}

Hope this solves a bit of your problem. If you face any error or have alternative to this one, let us know in the comment section below.

Leave a Reply

Your email address will not be published. Required fields are marked *

Psst. Yeah, you. Want some marketing secrets "gurus" never share?

Get them every month from your favorite teen entrepreneur - for free. After all, sharing is caring. ❤️🚀

🔒 No spam. I promise. 🔒