nodejs - JSON.stringify Error object

Question

I'm trying to convert Error object to JSON. However, the Error message seems to be lost.

try{
    require('someModule');
}catch(error){
    console.log(JSON.stringify(error)) //{"code":"MODULE_NOT_FOUND"}
}

Did I do anything wrong? How can I fix it?

It's not the error message being lost. What you just put in the comment is the full error object. — E_net4, Jul 28 '14 at 15:18

mscdex · Accepted Answer · 2014-07-28T17:36:13.393

12

The issue has to do with the fact that some of the properties set on Errors are configured as non-enumerable.

Here's something you can use to properly stringify Error objects, it sets a toJSON() method that JSON.stringify() looks for when converting an object:

var config = {
  configurable: true,
  value: function() {
    var alt = {};
    var storeKey = function(key) {
      alt[key] = this[key];
    };
    Object.getOwnPropertyNames(this).forEach(storeKey, this);
    return alt;
  }
};
Object.defineProperty(Error.prototype, 'toJSON', config);

Then just use JSON.stringify() as normal.

edited Jul 28 '14 at 17:36

answered Jul 28 '14 at 15:23

mscdex

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Thanks for your explanation. By the way, is `var storeKey = function(key)` a typo? – user3828771 Jul 28 '14 at 15:41
@user3828771 Code is fixed now. – mscdex Jul 28 '14 at 17:36
It's important to note that this breaks mongodb client: https://jira.mongodb.org/browse/NODE-554 – Sebastian Nowak Feb 14 '16 at 10:48

nodejs - JSON.stringify Error object

1 Answers1