当在JavaScript中执行传入的回调函数时，是否可以确定是否可以调用某个函数？

Question

The question title basically says it all. I made this Fiddle to make it easy to test. Here's the code:

var test = function(callback) {
    console.log("callback() might call alert()");
    callback();
}

test(function() {
    alert("one");
});

Answer 1

Converting a function to a string returns the source code, you can search that with a regular expression.

var test = function(callback) {
    if (callback.toString().test(/\balert\s*\(/) {
        console.log("callback might call alert()");
    callback();
};

This isn't perfect, though. It won't work with:

var foo = alert;
test(function() {
    foo("Fooled you!");
});

It could also get a false positive if alert( appears in a string.

Answer 2

You can redefine function alert

  function alert(str) { console.log('Somebody call alert:'+str); } 

But IMHO it can't be definitely checked before call.