CODEWITHSUNDEEP
javascriptnode.jsnullundefinedecmascript-2016
Don Rajitha Dissanayake
Don Rajitha Dissanayake

Reputation: 146

Can a null value automatically occur in JS

In JS an "undefined" value could occur automatically by mistake.(eg:- if you call a function which does not return any thing)

Can a "null" value occur automatically?

Upvotes: 0

Views: 278

Answers (1)

jfriend00
jfriend00

Reputation: 707706

undefined is what is returned when you attempt to access a property that is not there or an array value that is not there. It is also the initial value of a variable that has been declared, but not assigned a value yet. These are not really mistakes, but the way the language is designed when you request a value that is not there.

null does not occur by default like undefined does. If a variable or property or return value is null, that is because some programmer or API specifically assigned or returned null.

Also, calling a function that does not exist throws a ReferenceError.

Upvotes: 2

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