Is there any way to call an action when the method does not exist in a javascript object?

Question

In PHP, we have some special methods that can be included in a class.

One of them is the __call, that causes an action to be invoked (through it) when a method does not exist in a class.

Example:

class Exemplo
{
    public function existe()
    {
        echo 'Eu existo';
    }

   public function __call($method, $parameters)
   {
       echo "$method não existe, mas vou fazer alguma coisa legal";
   }
}

$e = new Exemplo;

$e->existo(); // 'Eu existo'

$e->nao_existo(); // "nao_existo não existe, mas vou fazer alguma coisa legal"

In javascript there is some way to do this?

Example:

function special(){}

special.prototype.existe = function () {
     console.log('Esse método existe');
}

Answer 1

There is no widely supported implementation equivalent to the _call function of PHP in Javascript.

In Ecmascript 2015 (ES6), there is a new implementation that will allow something like __call, the Proxy. However, not all browsers have already implemented this object. At the moment, only Firefox and Edge support Proxy.

As the Mozilla example, it is used this way:

var handler = {
    get: function(target, name){
        return name in target?
            target[name] :
            37;
    }
};

var p = new Proxy({}, handler);
p.a = 1;
p.b = undefined;

console.log(p.a, p.b); // 1, undefined
console.log('c' in p, p.c); // false, 37

Firefox supported a non-standard function that allowed this. However, since version 39, it is no longer supported. See Object.prototype. __noSuchMethod__

var obj = {};
obj .__noSuchMethod__ = function (name, args) {
    alert(name);
    alert(args);
}

obj.teste("teste1");

Answer 2

Invocation of functions in Types that are not functions generates error in Javascript.

That is to use () at the end of a variable or property that is not a function gives error and there is a tool as apparently PHP has.

How to get around this?

Well, this will have to be done in code, preventing errors.

You can check whether the variable or property is a function:

function foo(){
    // fazer algo
}

if (typeof foo === "function") foo();

Use a method to run functions. At the bottom there is already .call or .apply, but you can create your own:

function corredor(fn, argumentos, fallback) {
    var func = typeof fn === "function" ? fn : fallback;
    return func.apply(this, argumentos);
}

var foo = 'string';
var retorno = corredor(foo, [1, 2, 3], function () {
    return [].reduce.call(arguments, function (a, b) {
        return a + b;
    });
});
console.log(retorno);

jsFiddle: http://jsfiddle.net/txovxymd/