Difference between null and undefined (explained in 5 seconds)
null says
there is absolutely nothing.
undefined says
there should be something but I have nothing.
This is why the following function returns undefined when the argument is passed nothing because it means the function needs something but it has ...
csdal.hashnode.dev1 min read
Purvi Barot
undefined means a variable has been declared but has not yet been assigned a value.
var TestVar; alert(TestVar); //shows undefined alert(typeof TestVar); //shows undefinednull is an assignment value. It can be assigned to a variable as a representation of no value.
var TestVar = null; alert(TestVar); //shows null alert(typeof TestVar); //shows objectFrom the preceding examples, it is clear that undefined and null are two distinct types: undefined is a type itself (undefined) while null is an object.