确保一次只运行一个setTimeout（处于活动状态）？

本文介绍了确保一次只运行一个setTimeout（处于活动状态）？的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述 标签中递归的 setTimeout 函数getRandomProducts被称为 onload ，所以不断重复。< 函数setCategoryTree被从导航栏的嵌套ul中的链接调用 onclick 。 然后这个函数将变量mainCategory传递给getRandomProducts，其中变量被全局声明以维持它的初始化。所以，我试图做的是在导航栏中单击链接时重置getRandomProducts函数，并从单击的链接传递类别名称。但是， clearTimeout 似乎没有工作，所以迭代的发生频率更高，因为同时执行多个递归循环。 /> 不仅如此，而且我的全局变量并不像预期的那样存储来自setCategoryTree的数据（基本上我试图使用全局变量类似于静态变量）。我用 window.alert 分辨出了所有这些行为。 以下是相关的Javascript代码：

var mainCategory =; //从setCategoryTree 初始化var category = mainCategory; function getRandomProducts（category） { //window.alert(category）; if（typeof category ==undefined） category =all; else clearTimeout（t）; var req = new XMLHttpRequest（）; var products = document.getElementById（products）; req.onreadystatechange = function（） { if（（req.readyState == 4）&&（req.status == 200）） { var result = req.responseText; products.innerHTML = result; req.open（GET，default.php？category =+ category，true）; req.send（null）; var t = setTimeout（getRandomProducts（），1000）; } 函数setCategoryTree（link） { var categoryTree = document.getElementById（categoryTree）; / *使用DOM树来获取类别名称（innerHTML中最高的a标签）* / mainCategory = link.parentNode.parentNode.parentNode.getElementsByTagName（a ）[0] .innerHTML; var subcategory = link.innerHTML; categoryTree.innerHTML = - & nbsp; + mainCategory +& nbsp;& nbsp; - & nbsp; +子类别; getRandomProducts（mainCategory）;

解决方案

code> t 。下一次调用这个函数时，var t 将不可用。

因此，设置变量上面的函数（不包含在其中）

var randomProductsTimeout = false; function getRandomProducts（category）{ randomProductsTimeout = setTimeout（）[..]

The recursive setTimeout function getRandomProducts is called onload in the html body tag, and so is constantly iterating.The function setCategoryTree is being called onclick from the links in a nested ul of a navigation-bar. This function then passes the variable mainCategory to getRandomProducts, in which the variable is declared globally to maintain its' initialization....So, what I am trying to do is reset the getRandomProducts function when a link is clicked in the navigation-bar, and pass the category name from the link that was clicked. However, clearTimeout does not seem to be working and so the iterations occur a lot more frequently as there are then multiple recursive loops executing simultaneously.And not only that, but my global variables are not storing data from setCategoryTree as intended (basically I am trying to use the global variable similarly to a static-variable). I have discerned all of this behavior with the window.alert that is commented out.Here is the relevant Javascript code:

var mainCategory = ""; // initialized from setCategoryTree var category = mainCategory; function getRandomProducts(category) { //window.alert(category); if(typeof category == "undefined") category = "all"; else clearTimeout(t); var req = new XMLHttpRequest(); var products = document.getElementById("products"); req.onreadystatechange = function() { if( (req.readyState == 4) && (req.status == 200) ) { var result = req.responseText; products.innerHTML = result; } } req.open("GET", "default.php?category=" + category, true); req.send(null); var t = setTimeout("getRandomProducts()", 1000); } function setCategoryTree(link) { var categoryTree = document.getElementById("categoryTree"); /* climbing the DOM-tree to get the category name (innerHTML of highest "a" tag) */ mainCategory = link.parentNode.parentNode.parentNode.getElementsByTagName("a")[0].innerHTML; var subcategory = link.innerHTML; categoryTree.innerHTML = "--&nbsp;" + mainCategory + "&nbsp;&nbsp;--&nbsp;" + subcategory; getRandomProducts(mainCategory); }

解决方案

You are setting the variable t within the function. The next time this function gets called the var t will not be available for you.

Therefore, Set the variable above the function (not in it)

var randomProductsTimeout = false; function getRandomProducts(category){ randomProductsTimeout = setTimeout()[..]