litr

litr evaluates JavaScript literals. litr doesn't use eval and is safe to use.

Internally, litr is a thin wrapper around a PEG.js parser, generated from a stripped-down version of the PEG Javscript Grammar.

example

const litr = require('litr');

const someJsString = `[
    { name: 'Venus', mass: 4.8675e+24,  flags: 0b1101, population: 0, },
    { name: 'Earth', mass: 5.97237e+23, flags: 0b1000, population: 7734484600n, },
]`;

try {
    const result = litr.parse(someJsString);
    console.log(result);
} catch(err) {
    console.log('SYNTAX ERROR!', err.message);
}

> [
>   { name: 'Venus', mass: 4.8675e+24, flags: 13, population: 0 },
>   { name: 'Earth', mass: 5.97237e+23, flags: 8, population: 7734484600n }
> ]

use cases

• convert big amounts of data from Javascript to JSON
• deal with servers and APIs that return Javascript
• using user-provided data in calculations
• configuration files that contain values not easily expressed in JSON, e.g. regexes or bigints

what is supported

• decimal number literals (plain and scientific notation)
• hex, octal and binary literals
• BigInt literals (123456n)
• "signed" number literals (+123, -0xFEFE)
• single and double quoted strings, including "wide" unicode escapes, e.g "\u{1F44F}"
• RegExp literals (no validity check)
• arrays (with "elisions") and objects

usage

npm install litr

For browsers, grab litr.js.

litr provides a single function parse(string) which returns a Javascript value on success or throws a SyntaxError on failure.