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我正在用 HTML/Javascript 编写 Google Chrome 的扩展。我正在尝试使用全局变量在两个函数之间传递信息，但是即使我在一个函数中分配了我的变量，当我从另一个函数中读取它时它也没有改变。

    var type = 0; //define global variable
    window.onload=function(){onCreated()}; //set onCreated function to run after loading HTML

    function onCreated()
    {
        chrome.history.search({'text': ''},function(historyItems){gotHistory(historyItems)});//search for historyItems and then pass them to the gotHistory function
    }

    function gotHistory(historyItems)
    {
        var idcount=0;//used to increment the ids of each new element added
        for(var count=0; count < historyItems.length; count++)//go through each history item
        {
            chrome.history.getVisits({'url':historyItems[count].url}, function(visitItems){gotVisits(visitItems)}); //search for visitItems for the url and pass the results to gotVisists function (atm all this function does is assign the global variable to =3)

            var body = document.getElementById("outputid");//find the body of the HTML
            var newt = document.createElement("p");//create a new element
            newt.setAttribute("id","url"+idcount);//give it a unique id

            newt.innerHTML = historyItems[count].title;//set the text to say the title of the url

            if(type != 0)//if the other function was successful, type=3 and the text should be green
            {
                newt.style.color="green";
            }   

            body.appendChild(newt);//add the new element to the body
            idcount++;

        }
    }
    function gotVisits(visitItems)
    {
//assign the global variable to be 3
        type = 3;
    }

但是，元素永远不会是绿色的。它们应该始终是绿色的。这意味着在函数 gotVisits 中，类型未成功分配给 3。谁能解释这里发生了什么？

干杯，

Matt ps 我意识到 gotVisits 函数在这里真的没用，但我用它来说明一点。实际上，我将使用它将有用的信息传回给

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2 回答 2

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而不是：

var type = 0;

尝试：

window.type = 0;

或者，您还可以使用闭包，例如：

(function() {

var type = 0;

    var type = 0; //define global variable
    window.onload=function(){onCreated()}; //set onCreated function to run after loading HTML

    function onCreated()
    {
        chrome.history.search({'text': ''},function(historyItems){gotHistory(historyItems)});//search for historyItems and then pass them to the gotHistory function
    }

    function gotHistory(historyItems)
    {
        var idcount=0;//used to increment the ids of each new element added
        for(var count=0; count < historyItems.length; count++)//go through each history item
        {
            chrome.history.getVisits({'url':historyItems[count].url}, function(visitItems){gotVisits(visitItems)}); //search for visitItems for the url and pass the results to gotVisists function (atm all this function does is assign the global variable to =3)

            var body = document.getElementById("outputid");//find the body of the HTML
            var newt = document.createElement("p");//create a new element
            newt.setAttribute("id","url"+idcount);//give it a unique id

            newt.innerHTML = historyItems[count].title;//set the text to say the title of the url

            if(type != 0)//if the other function was successful, type=3 and the text should be green
            {
                newt.style.color="green";
            }   

            body.appendChild(newt);//add the new element to the body
            idcount++;

        }
    }
    function gotVisits(visitItems)
    {
//assign the global variable to be 3
        type = 3;
    }

})();

这样可以避免污染window对象，无论如何都应该避免这样做，并允许内部函数访问type变量。

它应该做你想做的事。

您的外部函数包装器window.onload也是多余的，只需执行以下操作：

window.onload = onCreated;
于 2013-01-26T00:14:06.990 回答
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它看起来像chrome.history.getVisits异步执行回调，所以您首先尝试检查该变量，稍后会更新它。您可以使用一对console.log消息来验证这一点。

将其余代码移动到回调中，以便在正确的时间执行。

于 2013-01-26T00:21:38.880 回答