setInterval()不重复.只工作1次 [英] setInterval() not repeating. Works only 1 time

问题描述

我正在尝试通过其自身更改div的left属性-当您将鼠标悬停在div上时，每秒更改一次，所以我这样做了:

I'm trying to have a div's left property change by its self - one every second when your hovering over so I made this:

$("div.scroll_left").hover(function(){
    var left_num = $('div.license_video').css("left")
    var left_num1 = parseInt(left_num, 10) - 1;
    var timerID = setInterval(alert(left_num1), 1000);
    //var timerID = setInterval(slideleft(left_num1), 1000);
},function(){
    clearInterval(timerID);
});
//function slideleft(left_num){
    //$('.license_video').css('left', left_num + "%");
//}

理论上，您会认为它会重复执行，直到您将光标移开以清除间隔为止.当我将鼠标悬停在它上面时，它一次不会重复(没有错误).然后，当我将鼠标悬停时，会出现错误未捕获的ReferenceError:未定义timerID"

In theory you would think it repeat till you move your cursor off which clears the interval. When I hover over it does it one time and never repeats (there are no errors). Then when I hover off it gives a error "Uncaught ReferenceError: timerID is not defined"

推荐答案

因此，您在这里遇到了两个不同的问题:

So you've got two different problems here:

// (1) timerID needs to be defined in a scope accessible to both hover callbacks
var timerID = null;

$("div.scroll_left").hover(function(){
    var left_num = $('div.license_video').css("left")
    var left_num1 = parseInt(left_num, 10) - 1;

    // (2) Pass a *function* to setInterval
    timerID = setInterval(function () {
        alert(left_num1)
    }, 1000);
}, function(){
    clearInterval(timerID);
    timerID = null;
});

写作时

setInterval(alert(left_num1), 1000);
// or
setInterval(slideleft(left_num1), 1000);

您正在将分别调用alert()或slideleft()的返回值传递给setInterval.您不传递函数本身.

you are passing the value returned by calling alert() or slideleft() (respectively) to setInterval. You are not passing the function itself.

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