uneval "polyfill"

uneval.es6

let uneval = (o, noNativeFns = true) => {
    var retVal = '';
    if (typeof o === 'object') {
        if (Array.isArray(o)) {
            retVal = '[' + o.map((el) => uneval(el)).join(',') + ']';
        } else if (o instanceof RegExp) {
            retVal = o.toString();
        } else if (o instanceof Date) {
            retVal = `new Date(${o})`;
        } else if (o === null) {
            retVal = 'null';
        } else if (Number.isNaN(o)) {
            retVal = 'NaN';
        }else {
            //[TODO] add support for defineProperty & getters & setters
            retVal = '{' + Object.keys(o).map((k) => `"${k}":${uneval(o[k])}`).join(',') + '}';
        }
    } else if (typeof o === 'function') {
        let isNative: boolean = o.toString().match(/^function \(\) \{ \[native code\] \}$/);
        if (isNative && noNativeFns) {
            throw new Error('No native functions is allowed');   
        }
        
        retVal = `(${isNative ? o.name : o.toString()})`;
    } else {
        retVal = JSON.stringify(o);
    }
 
    return retVal;
};

By using eval(uneval(some_value)) to test this uneval function, it will fail on following values:

1. (void 0)
2. -0
3. Infinity, -Infinity
4. NaN
5. [, ,]
6. new Date(1)
7. (function () { var x = {}; x.x = x; return x }())
8. Object(1), Object(''), Object(false)
9. (function () { p = function () {}; p.toString = function () { return 'alert(/xss/)' }; return p; }())
10. ({})