javascript delete keyword not working properly - Stack Overflow

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This is really weird I think, I have this json being sent through http.

{
   "foo":"bar",
   "foo2":"bar2",
   "name":{
       "firstName":"Joff",
       "middleName":"Ramirez",
       "lastName":"Tiquez"
   }
}

On the server I was performing these mands:

var data = req.body; // the json from http
console.log('data', data); // the data now has the req.body's value 
delete data.name; // <-- here's the delete
console.log('data', data); // the name object will obviously be deleted
console.log('req.body', req.body); // the name on the req.body was deleted too. Wtf?

So when I tried to use the req.body.name on the other parts of my program, the name is now gone. Is that how delete is supposed to work?

This is really weird I think, I have this json being sent through http.

{
   "foo":"bar",
   "foo2":"bar2",
   "name":{
       "firstName":"Joff",
       "middleName":"Ramirez",
       "lastName":"Tiquez"
   }
}

On the server I was performing these mands:

var data = req.body; // the json from http
console.log('data', data); // the data now has the req.body's value 
delete data.name; // <-- here's the delete
console.log('data', data); // the name object will obviously be deleted
console.log('req.body', req.body); // the name on the req.body was deleted too. Wtf?

So when I tried to use the req.body.name on the other parts of my program, the name is now gone. Is that how delete is supposed to work?

• javascript

Share Improve this question Follow asked Aug 16, 2016 at 11:59 jofftiquezjofftiquez 7,7081010 gold badges7070 silver badges122122 bronze badges 5

• 6 Objects are passed by reference, reqBody is the same object as the data – Dellirium Commented Aug 16, 2016 at 12:00
• WhyTH down vote? HAHA, It's a pretty valid question. lol – jofftiquez Commented Aug 16, 2016 at 12:05
• @Dellirium what do you mean "passed by reference"? So am not creating a new object when I passed req.body to data? Wow, my whole life was a lie. LOL – jofftiquez Commented Aug 16, 2016 at 12:08
• Thanks guys! This is really mind blowing. LOL – jofftiquez Commented Aug 16, 2016 at 12:12
• 1 When you "set the value" of a variable to an object, what you are doing is setting a pointer to a location in memory. So if you have an object, and you set reqBody to be that object, you are only copying the address. Then later you copy the address into data. After that you access data and remove the name from that address, but reqBody is still REFERENCING the same location in memory. There is only 1 object in your memory, and 2 variables each holding the same address to that object – Dellirium Commented Aug 16, 2016 at 12:15

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4 Answers 4

Sorted by: Reset to default 6

var data = JSON.parse(JSON.stringify(req.body));
delete data.name; // <-- here's the delete

Now when you do a

console.log('req.body', req.body); // This won't be deleted. 

As pointed out by @Dellirium, Objects are passed by reference, reqBody is the same object as the data

Is that how delete is supposed to work?

Yes. delete deletes properties from objects.

… but that isn't where your confusion is ing from.

var data = req.body;

The assignment operator copies the value of req.body and that value is a reference to an object (JS only ever gives you a reference to an object to play with).

When you copy that reference to data you have two references pointing to the same object. When you delete a property from the object, it is removed from the object and it doesn't matter which reference to that object you use.

See this question for some information about making a deep copy of an object.

You need to save data in other variable 1 by 1 object if you want to delete in same way.

Because when you use any object to assign in other object then value assign by reference. for more please check- this link

For your problem solution put values 1 by 1.

Yes it is. Delete keyword deletes the property of the instance itself.

EDIT: Objects are passed by reference. Consider copying the object, so the changes you do will only affect the object you're changing.

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