Problems with setInterval

I am just trying to implement the most basic example of setInterval with jQuery and am having problems. What's wrong here?

It says function rotate is not defined.

$(document).ready(function() {
    var speed = 5000;
    var run = setInterval("rotate()", speed);

    funct开发者_运维问答ion rotate() {
        alert ('rotate');
    }
});

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Do this instead:

$(document).ready(function() {
    var speed = 5000;

    function rotate() {
        alert ('rotate');
    }

    var run = setInterval(rotate, speed);
});

You could also simply do this:

$(function() {
    var speed = 5000;

    var run = setInterval(function() {
        alert ('rotate');
    }, speed);
});

You should declare run outside the ready event handler if you wish to be able to clear the interval later though, since it will go out of scope otherwise.

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You are passing setInterval a string to eval. This is:

• Hard to debug
• Inefficient
• Ugly
• executed in a different scope

The function is limited in scope to the function it is defined inside.

Pass the function directly instead

    var run = setInterval(rotate, speed);

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omit the parenthesis and quotes around rotate in your setInterval call. You are giving it the function itself, not the name. It shouldn't matter the order that they go in.

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That's effectively eval-ing rotate in (what I believe is) its own context. Change it to

var run = setInterval(rotate, speed);

and it should be fine.

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or even put the rotate function outside the ready function.

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this works

$(document).ready(function() {
    function rotate() {
        alert ('rotate');
    }
    var speed = 5000;
    var run = setInterval(function() { rotate() }, speed);

});

---

$(function() {
   var speed = 5000;
   var rotate = function() {
      alert("rotate");
   };

   window.setInterval(rotate, speed);
});

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You need to define rotate in the global scope.

$(document).ready(function() {
    window.rotate = function() {
        alert ('rotate');
    }
    var speed = 5000;
    var run = setInterval("rotate()", speed);
});