Javascript对象属性不在范围内
[英]Javascript object property not in scope
问题描述
I seem to have a problem with objects' properties' scope. 
我似乎对对象的属性范围有疑问。 I would like to output each of the Message objects' title and message properties to a select element, but it is Not Working ! 我想将每个Message对象的title和message属性输出到select元素，但是它不起作用 ！ What am I doing incorrectly 我做错了什么
<html><head>
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.5.0/jquery.min.js"></script>
<script type="text/javascript">
$(function(){
function Message(title, message) {
this.title=title;
this.message=message;
this.getTitle = function(){
return this.title;
};
this.getMessage = function(){
return this.message;
};
}
var messages = new Array(
new Message("First Title", "This is the first message"),
new Message("Second Title", "This is another message")
);
function updateSelect () {
$("#cannedMessages_button").empty();
for (c in messages) {
// First try, with getters and setters
$("#cannedMessages_button").append($('<option>', { value : c.getMessage() , text : c.getTitle() }));
// Second try, directly
$("#cannedMessages_button").append($('<option>', { value : c.message , text : c.title }));
}
}
updateSelect();
});
</script>
</head><body>
<form><select id="cannedMessages_button"></select></form>
</body></html>
I can verify that the foreach is in fact running two iterations, but I cannot get the values out of the objects. 我可以验证foreach实际上正在运行两次迭代，但是我无法从对象中获取值。
2 个解决方案
解决方案1
1 已采纳 2012-01-30 14:31:22
don't use for (c in messages ). 不要for (c in messages ）。
in is for iterating over properties of an object, not for iterating over values in an array. in是用于遍历对象的属性，而不是用于遍历数组中的值。
Use the tried and true 使用久经考验的真实
for(var i = 0; i < messages.length; i++) {
...
}
Also, you are not putting your getTitle and getMessage methods on a prototype, which is kind of wasteful. 另外，您不会将getTitle和getMessage方法放在原型上，这是一种浪费。
解决方案2
0 2012-01-30 14:38:19
the syntax for the for in loop in js is : js中for in循环的语法是：
for(var key in obj)
{
var currentElement = obj[key];
}
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