JS：我可以在通过setInterval（）调用的函数（）中增加一个var吗？(JS: Can I increment a var inside a function() that gets call

JS：我可以在通过setInterval（）调用的函数（）中增加一个var吗？(JS: Can I increment a var inside a function() that gets called through setInterval()?)

我有一个函数change_background() ，我通过setInterval( change_background(), 5000 );从document.onload调用setInterval( change_background(), 5000 ); 每隔5秒改变我标题的背景。

在我写作的时候，我的功能是：每次调用时我如何增加num var？

function change_background(){ var element = document.getElementsByClassName('top'); element[0].style.backgroundImage = 'url( "media/image' + num + '.jpg" )'; //when num gets greater than the amount of images if( num > 2 ){ num = 0; } }//end change_background()

我只是在努力实现这种效果。 这甚至可能是我这样做的方式，我是否采取了错误的方式？

I have a function change_background() that I call from document.onload through a setInterval( change_background(), 5000 ); to change the background of my heading every 5sec's.

Where I'm stuck in writing my function is: How can I increment my num var every time its called?

function change_background(){ var element = document.getElementsByClassName('top'); element[0].style.backgroundImage = 'url( "media/image' + num + '.jpg" )'; //when num gets greater than the amount of images if( num > 2 ){ num = 0; } }//end change_background()

I'm just messing around trying to achieve this effect. Is this even possible the way I'm doing it, am I going the wrong way about it?

最满意答案

尝试这个：

var num = 0; // declaration function change_background(){ var element = document.getElementsByClassName('top'); element[0].style.backgroundImage = 'url( "media/image' + num + '.jpg" )'; num++; //when num gets greater than the amount of images if( num > 2 ){ num = 0; } }//end change_background()

Try this:

var num = 0; // declaration function change_background(){ var element = document.getElementsByClassName('top'); element[0].style.backgroundImage = 'url( "media/image' + num + '.jpg" )'; num++; //when num gets greater than the amount of images if( num > 2 ){ num = 0; } }//end change_background()