deserialise.js

Function.deserialise = function(key, data) {
    return (data instanceof Array && data[0] == 'window.Function') ?
        new (Function.bind.apply(Function, [Function].concat(data[1], [data[2]]))) :
        data
    ;
};
Function.prototype.toJSON = function() {
    var whitespace = /\s/;
    var pair = /\(\)|\[\]|\{\}/;

    var args = new Array();
    var string = this.toString();

    var fat = (new RegExp(
        '^\s*(' +
        ((this.name) ? this.name + '|' : '') +
        'function' +
        ')[^)]*\\('
    )).test(string);

    var state = 'start';
    var depth = new Array(); 
    var tmp;

    for (var index = 0; index < string.length; ++index) {
        var ch = string[index];

        switch (state) {
        case 'start':
            if (whitespace.test(ch) || (fat && ch != '('))
                continue;

            if (ch == '(') {
                state = 'arg';
                tmp = index + 1;
            }
            else {
                state = 'singleArg';
                tmp = index;
            }
            break;

        case 'arg':
        case 'singleArg':
            var escaped = depth.length > 0 && depth[depth.length - 1] == '\\';
            if (escaped) {
                depth.pop();
                continue;
            }
            if (whitespace.test(ch))
                continue;

            switch (ch) {
            case '\\':
                depth.push(ch);
                break;

            case ']':
            case '}':
            case ')':
                if (depth.length > 0) {
                    if (pair.test(depth[depth.length - 1] + ch))
                        depth.pop();
                    continue;
                }
                if (state == 'singleArg')
                    throw '';
                args.push(string.substring(tmp, index).trim());
                state = (fat) ? 'body' : 'arrow';
                break;

            case ',':
                if (depth.length > 0)
                    continue;
                if (state == 'singleArg')
                    throw '';
                args.push(string.substring(tmp, index).trim());
                tmp = index + 1;
                break;

            case '>':
                if (depth.length > 0)
                    continue;
                if (string[index - 1] != '=')
                    continue;
                if (state == 'arg')
                    throw '';
                args.push(string.substring(tmp, index - 1).trim());
                state = 'body';
                break;

            case '{':
            case '[':
            case '(':
                if (
                    depth.length < 1 ||
                    !(depth[depth.length - 1] == '"' || depth[depth.length - 1] == '\'')
                )
                    depth.push(ch);
                break;

            case '"':
                if (depth.length < 1)
                    depth.push(ch);
                else if (depth[depth.length - 1] == '"')
                    depth.pop();
                break;
            case '\'':
                if (depth.length < 1)
                    depth.push(ch);
                else if (depth[depth.length - 1] == '\'')
                    depth.pop();
                break;
            }
            break;

        case 'arrow':
            if (whitespace.test(ch))
                continue;
            if (ch != '=')
                throw '';
            if (string[++index] != '>')
                throw '';
            state = 'body';
            break;

        case 'body':
            if (whitespace.test(ch))
                continue;
            string = string.substring(index);

            if (ch == '{')
                string = string.replace(/^{\s*(.*)\s*}\s*$/, '$1');
            else
                string = 'return ' + string.trim();

            index = string.length;
            break;

        default:
            throw '';
        }
    }

    return ['window.Function', args, string];
};

example.js

test = {
    //make the function
    run : function name(x, y, z) { return this.a + x + y + z; },
    a : 2
};
//serialise it, see what it looks like
test = JSON.stringify(test) //{"run":["window.Function",["x","y","z"],"return this.a + x + y + z;"],"a":2}
test = JSON.parse(test, Function.deserialise)
//see if `this` worked, should be 2+3+4+5 : 14
test.run(3, 4, 5) //14

test = () => 7
test = JSON.stringify(test) //["window.Function",[""],"return 7"]
JSON.parse(test, Function.deserialise)() //7

test = material => material.length
test = JSON.stringify(test) //["window.Function",["material"],"return material.length"]
JSON.parse(test, Function.deserialise)([1, 2, 3]) //3

test = ([a, b] = [1, 2], {x: c} = {x: a + b}) => a + b + c
test = JSON.stringify(test) //["window.Function",["[a, b] = [1, 2]","{ x: c } = { x: a + b }"],"return a + b + c"]
JSON.parse(test, Function.deserialise)([3, 4]) //14

class Bob {
    constructor(bob) { this.bob = bob; }
    //a fat function with no `function` keyword!!
    test() { return this.bob; }
    toJSON() { return {bob:this.bob, test:this.test} }
}
test = new Bob(7);
test.test(); //7
test = JSON.stringify(test); //{"bob":7,"test":["window.Function",[""],"return this.bob;"]}
test = JSON.parse(test, Function.deserialise);
test.test(); //7