功能在Chrome中运行，但在Firefox中未运行，表示功能未定义

Question

This code runs perfectly in Chrome, but Firefox says the function tile1 is not defined. What could be the problem?

Also, is there any way to shorten this function? I have tried using a for-loop inside tile1 and also an if-else statement but I didn't succeed.

$('div.tile').each(function(index, element) {
  for(var i=0;i<=index;i++){

  var tile1=function(){
    var one ="div.tile div.one";
    var two =" div.tile div.two";
    var three = "div.tile div.three";
    if(index==0){
      one="div.tile div.one";
      two="div.tile div.two";
      three="div.tile div.three";
    } else {
      one ="div.tile div.one"+index;
      two ="div.tile div.two"+index;
      three ="div.tile div.three"+index;
    }
      var $one=$(one);
      var $two = $(two);
      var $three=$(three);
      var oneTop = $one.top;
      var twoTop = $two.top;
      var threeTop = $three.top;
      delayRate += 3000; // delayRate 5 sec (5000) by default 

     $one
       .delay(delayRate)
       .animate({top: "-100.5%"},300,easing);   
     $two
       .delay(delayRate)
       .animate({top:"0%"},300,easing);
     $three
       .delay(delayRate)
       .animate({top:"100.5%"},300,easing);     

     $one
       .delay(12000)
       .animate({top: "-200.5%"},300,easing);
     $two
       .delay(12000)
       .animate({top:"-100.5%"},300,easing);
     $three
       .delay(12000)
       .animate({top:"0"},300,easing);

     $one
       .delay(12000)
       .animate({top: "-100.5%"},300,easing);
     $two
       .delay(12000)
       .animate({top:"0"},300,easing);
     $three
       .delay(12000)
       .animate({top:"100.5%"},300,easing);

     $one
       .delay(15000-delayRate)
       .animate({top: "0"},300,easing);
     $two
       .delay(15000-delayRate)
       .animate({top:"100.5%"},300,easing);
     $three
       .delay(15000-delayRate)
       .animate({top:"200.5%"},300,easing);

     if(i==3){
       delayRate=0;
     }
   }
 }  
 window.setInterval(tile1, 3000);
});

As I called the function the index comes randomly like 0,3,1,2, and there are 4 divs that the index corresponds to.

Answer 1

The use of function statements in JavaScript is discouraged. Check out Mozilla's page on function scope which has a great section on function statements vs. function expressions, and states:

Functions can be conditionally defined using either //function statements// (an allowed extension to the ECMA-262 Edition 3 standard) or the Function constructor. Please note that such function statements are no longer allowed in ES5 strict. Additionally, this feature does not work consistently cross-browser, so you should not rely on it.

The fact that you are seeing differences between browsers with this code is not surprising.

Try

var tile1 = function () {
    ...
}

While this should work for you here, it does so only because variable definitions with var are hoisted. As JavaScript evolves and we start using let instead of var , your use of tile1 in the setInterval call outside the loop in which tile1 is defined won't work.

One of the problems that can occur is that when you use i inside the inner function, you are always referring to the single instance of i in the outer scope (the loop counter), whose value is always equal to index . (EDIT: I show how to fix this below.)

Always be very, very careful when defining functions inside a loop. You really need to understand closures and hoisting and related concepts. Is there any way that tile1 can be defined globally, outside the loop?

Regarding your question on simplifying the code structure, I think you would be okay with defining tile1 with var , but I don't think you need that inner loop with i . Try:

 $('div.tile').each(function(index, element) { var tile1 = function () { var one ="div.tile div.one"; . . . if (index === 3) { // CHANGED I TO INDEX HERE. delayRate=0; } } window.setInterval(tile1, 3000); }); 

I'm not sure what the inner loop was buying you.

ASIDE: There is an effort underway for future JavaScript versions to deal with function statements in a block scope; you can see here that this is supported by certain versions of Chrome, but not Firefox.

ADDENDUM

Okay now I see that you want to cycle three steps in your tile1 function. While it is possible to put a for-loop inside the function, the JavaScript way is to have the function just run one step of its animation each time. If it needs some kind of counter, the counter should be external. One way to do this is like this:

var tile1 = function (i) {
  .
  .
  // use the value i here as needed
  .
  .
  setTimeout(function () {tile1((i + 1) % 3)}, 3000);
};
tile1(0);

What this does is it first calls your tile function with the value 0. Then after you do what you want at 0, you will schedule the next frame to run 3 seconds later with the i = 1. Then three seconds or so later with 2, then three seconds or so later with 0.

There is a little drift here, so you might want to use setInterval . This requires a closure. The form of the solution is this:

(function () {
  var i = 0;
  var tile1 = function () {
    .
    .
    // use the value i here as needed
    .
    .
    i = (i + 1) % 3;
  };
  setInterval(tile1, 3000);
}());

This code is pretty cool. It is a call of an anonymous function which calls setInterval to schedule the tile1 function to run every 3 seconds. Each time tile1 runs it uses the value of a non-local i which is hidden from the rest of the code with the closure. Each execution of tile1 uses the right value of i , then finishes by changing i to the proper value for its next invocation!

Both of these techniques are good to master in JavaScript. Have fun with them. The second one, of course, has no clock drift so it is probably better. To professionalize the code, you might want to assign the result of setInterval to a variable so you can call clearInterval at a later time.