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I'm using Mongoose with NodeJS. When I create new instance of a Model (called Expression), it adds the object to the database and returns me an object of the newly created model.

However.. I am unable to delete a field from this json object. 

var savedExpr = await Expression.create(expr);
delete savedExpr["__v"]
return savedExpr;

This code merely returns the original savedExpr with the __v field included. Any ideas?

Thank you.

Souleiman
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1 Answers1

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You can't delete some of these properties because they have been defined as "non-configurable".

 var savedExpr = await Expression.create(expr);
 var savedExprCopy = Object.assign({}, savedExpr);
 delete savedExprCopy["__v"];
 return savedExprCopy;

OR

 var savedExpr = await Expression.create(expr);
 savedExpr = savedExpr.toObject();
 delete savedExprCopy["__v"];
 return savedExprCopy;

Also an interesting thing just for knowledge, the __v attribute is set to true by default, you can disable the __v attribute in the Schema's definitions by setting version key option to false. E.g:

var expressionSchema = new Schema({ ... attributes ... }, { versionKey: false });
Helping hand
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  • Rats! I was confused because [typeof savedExpr] merely returned [object]... didn't realize toObject was needed! I was thinking of turning off versionKey, but decided to leave it to be safe. Thank you for the detailed answer. – Souleiman Jul 30 '18 at 20:18