delete operator does not actually delete the variable

Question

May I know why it prompts 1 rather than undefined for the following javascript code?

function a(){
    var y=1;
    delete y;
    alert(y);
}

a();

Have you read the documentation for delete? It operates on a property of an object: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/delete — George Stocker, Jan 19 '16 at 01:23
Of course it doesn't. `delete` is for deleting properties: http://perfectionkills.com/understanding-delete/ — Bergi, Jan 19 '16 at 01:24
Duplicate of http://stackoverflow.com/questions/16963066/how-to-delete-a-variable — Andy, Jan 19 '16 at 01:26

score 2 · Answer 1 · answered Jan 19 '16 at 01:24

2

So, this would work:

var y = { val: 1};
delete y.val;
console.dir(y);

outputs:

{}

answered Jan 19 '16 at 01:24

George Stocker

score 1 · Answer 2 · answered Jan 19 '16 at 01:25

1

delete is only effective on an object's properties. It has no effect on variable or function names.

answered Jan 19 '16 at 01:25

Solci

2 Answers2