Convert arrow function into classic function in runtime

arrowFunctionToClassic.js

function isArrowFunction(f) {
    return typeof f == 'function' && /^\([^)]*\)\s*=>/.test(f.toString());
}

function arrowFunctionToClassic(f) {
 
    var string_function_converted = f.toString().replace(/\(([^)]*)\)\s*=>([\s\S]+)/, function(all, params, content) {
        if ( content.substr(-1) != '}' )
            content = '{return '+ content + ';}';
        return 'function('+params+')'+content;
    });

    return eval('(' + string_function_converted + ')');
}

function convertObjectArrowFunctionToClassic( object ) {
    for (var prop in object)
        if ( isArrowFunction(object[prop]) )
            object[prop] = arrowFunctionToClassic(object[prop]);
}




//////// TESTING

var obj = {
    n: 25,
    f1: function (a) { return this.n*a; },
    f2: function f2(a) { return this.n*a; },
    f3: (a) => this.n*a,
    f4: (a)=> {
        a*=2;
        return this.n*a;
    }
};



console.log('======= Before')
console.log(isArrowFunction(obj.f1), obj.f1(2)); // false 50
console.log(isArrowFunction(obj.f2), obj.f2.call({n:50}, 2)); // false 100
console.log(isArrowFunction(obj.f3), obj.f3(2)); // true NaN
console.log(isArrowFunction(obj.f4), obj.f4.call({n:50}, 2)); // True NaN

convertObjectArrowFunctionToClassic( obj );

console.log('======= After')
console.log(isArrowFunction(obj.f1), obj.f1(2)); // false 50
console.log(isArrowFunction(obj.f2), obj.f2.call({n:50}, 2)); // false 100
console.log(isArrowFunction(obj.f3), obj.f3(2)); // false 50
console.log(isArrowFunction(obj.f4), obj.f4.call({n:50}, 2)); // false 200