如何在Javascript中创建全局对象？
如何在Javascript中创建全局对象？
提问于 2014-06-24 20:06:38
我做了一个小的phonegap/cordova应用程序，我需要访问我的.js文件中的一个对象。事实证明，我不知道如何改变我的代码结构来实现这一点。
下面是我的index.html代码：
<!DOCTYPE html>
<html>
<head>
<title>NFC tag ID reader</title>
<script type="text/javascript" src="js/index.js"></script>
<script type="text/javascript" charset="utf-8">
// Wait for device API libraries to load
document.addEventListener("deviceready", onDeviceReady, false);
// device APIs are available
function onDeviceReady() {
window.requestFileSystem(LocalFileSystem.PERSISTENT, 0, gotFS, fail);
}
function gotFS(fileSystem) {
fileSystem.root.getFile("readme.txt", {create: true, exclusive: false}, gotFileEntry, fail);
}
function gotFileEntry(fileEntry) {
fileEntry.createWriter(gotFileWriter, fail);
}
function gotFileWriter(writer) {
writer.onwriteend = function(evt) {
console.log("contents of file now 'some sample text'");
writer.truncate(11);
writer.onwriteend = function(evt) {
console.log("contents of file now 'some sample'");
writer.seek(4);
writer.write(" different text");
writer.onwriteend = function(evt){
console.log("contents of file now 'some different text'");
}
};
};
writer.write("some sample text");
//MAKE THIS OBJECT GLOBAL ?
}
function fail(error) {
console.log(error.code);
}
</script>
</head>
<body>
<div class="app">
<script type="text/javascript">
app.initialize();
</script>
</body>
</html>下面是我的index.js代码：
var app = {
/* Application constructor */
initialize: function() {
this.bindEvents();
console.log("Starting NFC Reader app");
},
/* bind any events that are required on startup to listeners: */
bindEvents: function() {
document.addEventListener('deviceready', this.onDeviceReady, false);
},
/* this runs when the device is ready for user interaction: */
onDeviceReady: function() {
nfc.addTagDiscoveredListener(
app.onNfc, // tag successfully scanned
function (status) { // listener successfully initialized
app.displayCpt("<b>"+cpt+"</b>" + ' personnes restantes.');
app.displayBjr("\n");
app.displayBjr("Identifiez-vous:");
},
function (error) { // listener fails to initialize
app.display("NFC reader failed to initialize " +
JSON.stringify(error));
}
);
},
/* displays tag ID from @nfcEvent in message div: */
onNfc: function(nfcEvent) {
var tag = nfcEvent.tag;
var nfcUid = nfc.bytesToHexString(tag.id);
var myDb = {
"04c85ccab52880": {
"name": "name",
"firstname": "fname",
"societe": "work"
}
var mapped = Object.keys(myDb).map(function(uid){
return (myDb[uid].uid = uid) && myDb[uid];
});
for(var i = 0; i < mapped.length ; i++){
if(mapped[i]['uid'] != nfcUid){
mapped[i]['uid'] += 1;
} else {
mapped[i]['uid'] = nfcUid;
app.display(mapped[i]['name'] + ' ' + mapped[i]['firstname'] + ', ' + mapped[i]['societe']);
writer.write(mapped[i]['name'] + ' ' + mapped[i]['firstname'] + ', ' + mapped[i]['societe']);
//I WOULD NEED THIS WRITER USABLE IN ORDER TO WRITE MY ARRAY CONTENT INTO A FILE
}
}
},
}; // end of app我认为我的writer对象需要是全局的，才能使映射的数组写入文件，但我找不到这样做的方法。有什么想法吗？
谢谢
回答 1
Stack Overflow用户
发布于 2014-06-24 20:19:16
您是否尝试过将var writer放在所有内容之外，并将其从gotFileWriter(writer)的参数列表中删除？这应该使它成为一个全局变量。请注意，这并不是最佳的编程实践，应该尽可能避免使用全局变量。
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原文链接：
https://stackoverflow.com/questions/24386224
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