如何解决Undefined和Nan？ [英] How to resolve Undefined and Nan?
问题描述
我正在构建Chrome扩展程序，并在弹出窗口中遇到以下错误。
I清楚地定义了'total'变量，并在其中存储来自本地存储的值。但是，为什么我
得到这样的错误？
m试图做的：
<1>我将总变量存储在本地存储中，并从popup.js访问它。
2）然后修改popup.html中的< p> 元素
popup.html和popup.js：
$ b popup.js：
var total，percentage;
chrome.storage.local.get（'myVariable'，function（items）{
total =（items.myVariable）;
}）;
百分比=总数/ 7.25;
document.getElementById（total）。innerHTML = total;
document.getElementById（percentage）。innerHTML = percentage;
popup.html：
<！DOCTYPE HTML>
< html>
< head>
< title>弹出式页面< / title>
< / head>
< body>
< form name =F1method =POST>
TOTAL：< p id =total>< / p>
PERCENTAGE：< p id =percentage>< / p>
< / form>
< script src =popup.js>
< / script>
< / body>
< / html>
我的contentscript.js中的片段
chrome.storage.local.set（{
'myVariable'：total;
}）;
chrome.runtime.sendMessage（{
greeting：myAction
}）;
在background.js中，我有这个：
chrome.runtime.onMessage.addListener（
函数（request，sender，sendResponse）{
if（request.greeting ==myAction）{
collectData（）;
}
}）;
在访问本地存储之前，我们应该在popup.js中添加一个侦听器。我添加并检查，但
我得到相同的结果。
这段代码有什么问题？
如何完成我要做的事情？
我的扩展程序的本地存储：
var total，percentage;
chrome.storage.local.get（'myVariable'，函数（items）{
total =（items.myVariable）;
百分比=总数/ 7.25 ;
document.getElementById（total）。innerHTML = total;
document.getElementById（percentage）。innerHTML = percentage;
}）;
I'm building an Chrome extension and I encountered following error in my popup.
I clearly defined 'total' variable and storing in it a value from local storage.But why am I getting such an error?
What I'm trying to do:
1)I'm storing total variable in local storage and access it from popup.js.
2)Then modify <p> elements in popup.html
Here is popup.html and popup.js:
popup.js:
var total,percentage;
chrome.storage.local.get('myVariable', function (items) {
total = (items.myVariable);
});
percentage = total/7.25;
document.getElementById("total").innerHTML = total;
document.getElementById("percentage").innerHTML = percentage;
popup.html:
<!DOCTYPE HTML>
<html>
<head>
<title>Popup page</title>
</head>
<body>
<form name="F1" method="POST">
TOTAL : <p id="total"></p>
PERCENTAGE : <p id="percentage"></p>
</form>
<script src="popup.js">
</script>
</body>
</html>
Snippet from my contentscript.js
chrome.storage.local.set({
'myVariable': total;
});
chrome.runtime.sendMessage({
greeting: "myAction"
});
In background.js I've got this :
chrome.runtime.onMessage.addListener(
function (request, sender, sendResponse) {
if (request.greeting == "myAction") {
collectData();
}
});
Should we add a listener to popup.js before accessing local storage. I added and checked but I'm getting the same result. What's wrong with this code? How can accomplish what I'm set to do?
Local storage of my extension:
The chrome.storage.local.get callback is executed asynchronously so total doesn't get defined until after you try to use it. If instead move the rest of the script into the callback it should work.
var total,percentage;
chrome.storage.local.get('myVariable', function (items) {
total = (items.myVariable);
percentage = total/7.25;
document.getElementById("total").innerHTML = total;
document.getElementById("percentage").innerHTML = percentage;
});
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