Javascript clearTimeout 如果存在
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clearTimeout if exists
提问by Gerben
timer_gearexist only in case if I press some button (until 5 sec). But there is another function it can be called any time. In this function I clear the timer and restart it. But first I have to check if the object exists otherwise I get this error:
Uncaught ReferenceError: timer_gear is not defined
timer_gear仅当我按下某个按钮（直到 5 秒）时才存在。但是还有另一个函数可以随时调用。在这个函数中，我清除计时器并重新启动它。但首先我必须检查对象是否存在，否则我会收到此错误：Uncaught ReferenceError: timer_gear is not defined
Could you help me to solve this? These does not work.
你能帮我解决这个问题吗？这些都行不通。
if(timer_gear!="undefined")clearTimeout(timer_gear);
if(timer_gear)clearTimeout(timer_gear);
EDIT1: first I misspelled my question: if(!timer => if(timer EDIT2:
EDIT1：首先我拼错了我的问题： if(!timer => if(timer EDIT2:
the full code is:
完整代码是：
function hide_gear(){
$('#gear_div').animate({opacity: 0}, 1000);
delete timer_gear; //EDIT3: destroy object
}
...
...
/*gear*/
$('#gear').click(function(){
$('#gear_div').animate({
opacity: 1,
}, 1000, function() {
timer_gear = setTimeout("hide_gear();",5000);
});
});
$('#gear').mousemove(function(){
if( ? ? ? )
{
clearTimeout(timer_gear);
timer_gear = setTimeout("hide_gear();",5000);
}
});
Results:
结果：
timer_gear// Uncaught ReferenceError timer_gear is not defined
timer_gear != undefined // Uncaught ReferenceError: timer_gear is not defined
typeof timer_gear !== "undefined" // WORKS
typeof timer_gear != "undefined" // WORKS, just tired it
var timer_gear; //at the begining - WORKS, but I did not wanted a new variable if its not necessary
thank you for answers!
谢谢你的回答！
采纳答案by Rocket Hazmat
The 1st one should be:
第一个应该是：
if(typeof timer_gear !== "undefined"){
clearTimeout(timer_gear);
}
And the 2nd, but this won't workif timer_gearis not defined, so you should use the typeofone above:
第二个，但如果没有定义，这将不起作用timer_gear，所以你应该使用typeof上面的一个：
if(timer_gear){
clearTimeout(timer_gear);
}
回答by Gerben
All you need to do is declare timer_gear. clearTimeoutis not the problem here. To quote the MDN; Passing an invalid ID to clearTimeoutdoes not have any effect (and doesn't throw an exception). So just add the following to the top of your code:
您需要做的就是声明timer_gear。clearTimeout不是这里的问题。引用MDN；将无效 ID 传递给clearTimeout没有任何效果（并且不会引发异常）。因此，只需将以下内容添加到代码的顶部：
var timer_gear;
No need for all the if's that everyone else is suggesting.
不需要其他人建议的所有 if。
回答by Alex Turpin
If you only want to clear the timer held in the variable timer_gearif it exists, you can do
如果您只想清除保存在变量中的计时器（timer_gear如果存在），您可以这样做
if (timer_gear) clearTimeout(timer_gear);
回答by Xion
You need a different condition on your if:
你需要一个不同的条件if：
if (typeof(timer_gear) !== "undefined")
or simply:
或者干脆：
if (timer_gear)
回答by David Laberge
Normally that should work:
通常这应该工作：
timer_gear = false;
if(timer_gear != false){
clearTimeout(timer_gear);
}
回答by Nivas
if(timer_gear)clearTimeout(timer_gear);
or
或者
if(timer_gear != undefined)clearTimeout(timer_gear);
