Question

I wand to check for the existence of a JavaScript method, when I have a variable with that method name inside it.

使用购买力平价我可以这样做:

$method =  bar ;
$object = new Foo;
if(method_exists($object, $method))
{
    //Foo->bar()
}

我如何在 Java山这样做? 我的第一次尝试失败了:

var method =  bar ;
if(typeof(obj.method) != "undefined")
{
    obj.method();
}
else
{
    obj.default();
}

Answer 1

<>代码> 财产为<代码>功能”,使用<代码>method 缩略语反对:

((typeof obj[method] === "function") ? obj[method] : obj.default)();

Answer 2

I typically just do if(obj.method) {...} but you could always use a try/catch:

try {
    obj.method();
} catch(e) {
    // obj or obj.method didn t exist, so let s try plan b
    obj.planB();
}

Answer 3

  (obj[method] || obj.default)();

如果你想要一条一条线的话,也会奏效。

Answer 4

[ blah ] and .blah are equivalent in a Javascript Object, so you can call your method like

obj[method]();

Where method is a string containing the name of the method to call.

Answer 5

You should the object s method property to be typeof as function. E.g.

 if (typeof(obj[method]) == "function") {
   obj[method]();
 }

Here is a JSFiddle explaining how to check for a function.