Javascript删除运算符

Question

I read a book about javascript that said:

var o = {x:1 , y:2 };
delete o ; // Can't delete a declared variable so returns false;

However, the book also states that the variables declared outside any function scope are properties of the global object.

Why aren't we allowed to delete it then if it is a property of the global object?

Answer 1

By saying:

var o = {x:1 , y:2 };

in the top level scope, you are declaring a global variable , which can not be deleted. It does create a property on the global object (which is aliased to the window object in browsers), but it is a special property indeed. However, if you make the declaration like:

o = {x:1 , y:2 };

then you are setting a property on the global scope (remember, the window object) implicitly. The two are similar, but different enough. The delete operator removes an implicit property from an object, but will not delete a variable created on the global object.

Edit, found a more thorough answer

https://stackoverflow.com/a/4862268/1443478

Answer 2

Since O is already declared and have properties you cannot use delete on the object. You can use

var o = {x:1 , y:2 };
delete o.x ; 

and delete properties here is a DEMO for the same.

Answer 3

first you have to know what is the work of delete operator.let me explain---

"The delete operator removes a property from an object".here i say it removes an object property not a variable.

in your code you declare a variable.not an object so delete does not work.i think you understand.

o = {x:1 , y:2 }; delete o ;

but the code above is right i think. why? because here o is a property of the global object which is also an object so it work properly.the link which can help you is delete operator

it is my first answer.be happy with coding.