Uncaught TypeError: Cannot read property '' of undefined
JavaScript Error: Uncaught TypeError: Cannot read property '' of null
JavaScript TypeError is returned when an operand or argument passed to a function is incompatible with the type expected by that operator or function. This error occurs in the browser when you read a property or call a method on an undefined object.
There are a few variations of this error depending on the property you are trying to access. Sometimes instead of undefined it will output null:
Uncaught TypeError: Cannot read property '' of null
Cannot read property '' of undefined
Cannot read property '' of null
Simply put, undefined means that a variable has been declared but has not yet been given a value. This particular error is probably the easiest to understand from an undefined point of view, because undefined is not considered an object type at all (but its own undefined type instead), and properties cannot belong to only to objects in JavaScript.
This error occurs when we want to access a property on a variable whose value is undefined or null. This error occurs when you try to call a method or try to access a property of a variable that does not exist (is not an object).
Null vs. Undefined in JavaScript The value "undefined" indicates that a variable has been declared, but no value has been assigned. On the other hand, "null" refers to a non-existent object, which basically means "empty" or "nothing". These are two values generally used to indicate the absence of something. Also, undefined and null are two distinct types: undefined is a type itself (undefined) while null is an object.
Other Javascript errors :
- Cannot read property view
- Cannot read property words
- Cannot read property firstchild
- Cannot read property 1
- Cannot read property browserwindow
- Cannot read property mouse
- Cannot read property use
- Cannot read property zone
- Cannot read property extend
- Cannot read property name
- Cannot read property files
- Cannot read property document
- Cannot read property addeventlistener
- Cannot read property zindex
- Cannot read property query
- Cannot read property validate
- Cannot read property init
- Cannot read property setstate
- Cannot read property defaultview
- Cannot read property call
- Cannot read property pending
- Cannot read property y
- Cannot read property length
- Cannot read property join
- Cannot read property getelementsbytagname
- Cannot read property destroy
- Cannot read property keyup
- Cannot read property left
- Cannot read property prototype
- Cannot read property filter
- Cannot read property split
- Cannot read property msie
- Cannot read property dataset
- Cannot read property createelement
- Cannot read property append
- Cannot read property createdocumentfragment
- Cannot read property constructor
- Cannot read property play
- Cannot read property then
- Cannot read property click
- Cannot read property match
- Cannot read property getcontext
- Cannot read property json
- Cannot read property slice
- Cannot read property register
- Cannot read property addmethod
- Cannot read property innerhtml
- Cannot read property height
- Cannot read property browser
- Cannot read property render
- Cannot read property hasattribute
- Cannot read property each
- Cannot read property ajax
- Cannot read property display
- Cannot read property visible
- Cannot read property nodename
- Cannot read property value