Function in array is null in js

Question

I am having trouble with writing functions in arrays.

Here is what happens:

config.js

module.exports = {
  transformers: {
    reshape: {
      parser: 'sugarml',
      plugins: [
        // require('reshape-custom-elements')({defaultTag: 'span'})
        function () {
          console.log(arguments)
        }
      ]
    }
  }
}

Then in the node REPL

var config = require('./config.js')

console.log(JSON.stringify(config.transformers, null, 2))

It outputs

{
  "reshape": {
    "parser": "sugarml",
    "plugins": [
      null
    ]
  },
  "uglify-js": {
    "mangle": {
      "toplevel": true
    }
  },
  "rollup": {
    "format": "es",
    "plugins": {
      "rollup-plugin-node-resolve": {},
      "rollup-plugin-commonjs": {}
    }
  }
}

I am confused why plugins is [null]

It is not JSON if i require() it as a JS file, right? It is still a JS object — Caleb Eby
– Caleb Eby, Commented Jan 2, 2017 at 23:51
It is JSON as soon as you pass it (successfully) through JSON.stringify — Phil
– Phil, Commented Jan 2, 2017 at 23:52
Oh, right. I have an error that I thought was related to this, but it wasn't — Caleb Eby
– Caleb Eby, Commented Jan 2, 2017 at 23:57

Nick Tomlin · Accepted Answer · 2017-01-02 23:51:12Z

4

You cannot serialize a function in JSON. From MDN:

If undefined, a function, or a symbol is encountered during conversion it is either omitted (when it is found in an object) or censored to null (when it is found in an array). JSON.stringify can also just return undefined when passing in "pure" values like JSON.stringify(function(){}) or JSON.stringify(undefined).

source

I would question storing configuration like this in JSON, but if you really need to you can consider something like serialize-javascript that will handle the serialization of functions.

answered Jan 2, 2017 at 23:51

Nick Tomlin

29.4k12 gold badges65 silver badges95 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Function in array is null in js

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related