uneval.js

Convert an object to its source code (With circular references too!)

Always update to the latest version!

npm r uneval.js & npm i uneval.js

Usage

You can both import the package like this...

const uneval = require("uneval.js");

...and like this

const { uneval } = require("uneval.js");

Simply pass the function as an argument to obtain the source code and eval it to obtain the object again.

You additionally can give some options to personalize the output

const a = {};
a.b = a.c = { a, url: /^(\+0?1\s)?\(?\d{3}\)?[\s.-]\d{3}[\s.-]\d{4}$/ig };
a.e = a;
console.log(uneval(a, { tab: "  " }));

And the output will be

(x => (
  x[1] = {
    c: x[2] = {
      url: /^(\+0?1\s)?\(?\d{3}\)?[\s.-]\d{3}[\s.-]\d{4}$/gi
    },
    b: x[2]
  },
  x[2].a = x[1],
  x[1].e = x[1]
))({})

Note that the complexity of the output depends on the complexity of the input

console.log(uneval([1, { a: "hi" }], { pretty: false })) // [1,{a:"hi"}]

Options

Additionally to the object to stringify you can pass an option object to personalize your output. The available options are

• pretty
  • Setting it to false deactivates space, endl and tab
  • It defaults to true
• space
  • Set the string that will replace the spaces in the output
  • Setting it to false is like setting it to ""
  • It defaults to " "
• endl
  • Set the string that will replace the new lines in the output
  • Setting it to false is like setting it to ""
  • It defaults to "\n"
• tab
  • Set the string that will replace the tabs in the output
  • Setting it to false is like setting it to ""
  • It defaults to "\t"
• proto
  • Saves the class of objects (Including the __proto__ property)
  • It defaults to true
• safe
  • Wraps object literals in brackets to not confuse them with blocks
  • It defaults to true
• func
  • Put the top object in a function that defines the cache variable
  • It defaults to true
• val
  • The name of the variable which will cache the repeated references
  • It defaults to "x"

Supported

• All the things supported by json
• Multiple references (Even in Symbol keys)
• Circular references (Are much worse, trust me)
• undefined
• NaN, Infinity, -Infinity
• Symbols
• Symbol keys
• Functions
• Regular Expressions
• Maps
• Sets
• Dates
• "Objectified primitives", like new String("hello")
• Big Integers
• Custom types

Unsupported (Or at least not completely)

• Proxies (If you know how to extract the [[Target]] and the [[Handler]] of a proxy tell me)
• Clojures (Functions that access external local variables)

Coming Soon (Hopefully) in order of probability

2. Arrays and Functions custom fields
3. Non enumerable properties
4. Getters and Setters
5. New syntax for object's methods, like { func() {} }

Known Problems

(I don't know how to put issues on github 😳)

• The references to a primitive version of a symbol are not detected

  const a = Symbol("hi");
  const b = eval(uneval({
      c: Object(a),
      d: a
  }));
  console.log(b.c === b.d); // false

• If an object of special type (Such as String, Date, ...) contains the first reference to an other object, that object will become undefined everywhere

  const a = new Date();
  a.b = {};
  console.log(eval(uneval({
      a,
      b: a.b
  }))); // { a: 2021-08-16T02:57:10.125Z, b: undefined }