Loading "Grunt-karma.js" Tasks...error >> Typeerror: Cannot Read Property 'prototype' of Undefined
Uncaught TypeError: Cannot read property of undefined In JavaScript
Posted by Deeksha Agarwal | March 27, 2018
Debug • JavaScript • Miscellaneous •
47250 Views | 2 Min Read
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 mistake most frequently than not is faced when the scripts come up across uninitialized variable or object.
Description
'Undefined' is the property of the global object. If y'all don't assign any value to a variable is of blazon 'undefined'. A code also return the undefined value when the evaluated variable doesn't have any assigned value.
Code structure
| office test ( t ) { //defining a role if ( t === undefined ) { //if t=undefined, call tt console . log ( t . tt ) //phone call tt fellow member from t } return t ; } var a ; //a is a variable with undefined value console . log ( test ( a ) ) ; //part call |
Error
When you run this lawmaking, you'll get:
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 examination ( t ) { //defining a office if ( t === undefined ) { //if t=undefined, call tt console . log ( t ) //call t } render t ; } var a = 10 ; //a is a variable with undefined value console . log ( exam ( a ) ) ; //function call |
After I assign a value to a, the function volition return me the value of t, mapped by a=10.
Output
Catch Before It Happens.
Power to piece of work with uninitiated variables/objects is one of the plus points of JavaScript over other languages like Java, C etc. And so many times developers are tempted to use this feature, fifty-fifty though it not a very good practice. So if y'all are a programmer that is addicted to not initializing the variables, you tin at least endeavor to grab the issues before they happen through simple statement
| if ( typeof ( jsvariable ) == 'undefined' ) { . . . } |
Hope this solves a bit of your trouble. If you face up any mistake or have alternative to this one, let us know in the comment section below.
Written by Deeksha Agarwal
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Source: https://www.lambdatest.com/blog/undefined-type-error-in-javascript/
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