uneval

Overcome JSON.stringify limitations.

What is uneval

uneval is a function turning a JavaScript value into a string that can be evaluated.

It exists to overcome JSON.stringify limitations. But you should better use JSON.stringify and avoid using uneval at all. However, if some JSON.stringify limitations is a problem for you uneval might be what you're looking for.

JSON.stringify limitations

• Transforms regexp into {}

JSON.stringify(/foo/) === "{}"

• Transforms -0 into 0

JSON.stringify(-0) === "0"

• Transforms NaN into null

JSON.stringify(NaN) === "null"

• Transforms Infinity into null

JSON.stringify(Infinity) === "null"

• Does not support circular structure

const value = {}
value.self = value
try {
  JSON.stringify(value)
} catch (error) {
  error.name === "TypeError"
}

• Transforms dates into strings

JSON.stringify(new Date(0)) === `"1970-01-01T00:00:00.000Z"`

• Is not optimized for repetitive structure

JSON.stringify(["very-long-string", "very-long-string"]) ===
  `["very-long-string","very-long-string"]`

"very-long-string" is repeated twice. It can becomes a waste if you use it to stringify very big structures.

• Ignores non enumerable properties

JSON.stringify(Object.defineProperty({}, "foo", { enumerable: false })) === "{}"

How to use

npm install --save-dev @dmail/uneval

See browser and node examples below.

browser example

<script src="https://unpkg.com/@dmail/[email protected]/dist/global/main.js"></script>
<script>
  const { uneval } = window.__dmail_uneval__
  console.log(eval(uneval({ answer: 42 })))
</script>

node example

const { uneval } = require("@dmail/uneval")

console.log(eval(uneval({ answer: 42 })))

Interactive browser example

— see https://dmail.github.io/uneval/browser-example.

Interactive node example

— see https://dmail.github.io/uneval/node-example