javascript setInterval的内存泄漏

Question

Is there any difference between these 2 statements

setInterval(animateImage, 1000);

or 

setInterval('animateImage()', 1000);

Will the second statement be interpreted by the browser js engine is any different way that could cause memory leak or performance issues. Same is the case with the setTimeout() call. The application makes use of 4 timer calls with 1-2 sec intervals.

Answer 1

The biggest difference is that the second statement will cause animateImage() to be evaluated in global scope.

This can lead to problems if

• animateImage is not in global scope
• animateImage has to access variables that are not in global scope

Eg the following will not work:

function foo() {
    var answer = 42;
    function bar() {
        alert(answer);
    }
    setTimeout('bar()', 1000);
}

foo();

Actually there is never a reason to use the second statement, so the question about memory leaks is not relevant anymore ;)

And obviously, passing a direct reference to a function will be 'faster' than eval uating a string.

Answer 2

Use the first one. It makes debugging nicer since there's no eval'd code involved, it is faster and cleaner. Eval is evil and it's good to avoid it whenever possible.

In case you ever need to pass an argument, use the following code:

setInterval(function() {
    animateImage(...);
}, 1000);

Answer 3

The second statement will probably be slightly slower and use more memory, but it wouldn't be significant either way. You should Use the first one regardless, because it's generally best to avoid using eval .

Answer 4

I don't think so. You want to use callbacks to avoid memory leaks.

Answer 5

I recommend using it like so:

setInterval(function(param1, param2){animateImage(param1, param2)}, 1000);

to pass parameters instead of passing them at the end