Opera，For In Loop，相同的键出现两次 [英] Opera, For In Loop, Same Key Appears Twice
问题描述
标题说。如果我在HTML集合中使用for循环，我会两次获得
长度。
<！DOCTYPE HTML>
< html lang =" en">
< head>
< title>长度两倍< / title>
< / head>
< body>
< form action =" javascript ：;" id =" form1">
< input name =" length" type =" text" />
< / form>
< script type =" text / javascript">
var f = document.forms [0] .elements，a = [];
for（p in f）{
a.push（''"' '+ p +''"：''+ f [p]）;
}
document.write（"< xmp>" + a.join （"，\ n"）+"<" +" / xmp>"）;
< / script>
< /正文>
< / html>
Opera：
" 0" ：[object HTMLInputElement]，
" length" ：[object HTMLInputElement]，
" length" ：[object HTMLInputElement]，
" item" ：function item（）{[native code]}，
" namedItem" ：function namedItem（）{[native code]}，
" tags" ：function tags（）{[native code]}
但是，如果名为-length-的元素是
，则长度只会出现两次。否则，长度属性只出现一次，并且具有
" normal"表单控件数量的值。
这里可能发生什么？我怀疑
中的对象可能是带有 - length - 属性的原型，但是无法验证这一点。
hasOwnProperty总是返回false。
加勒特
dhtml写道：
标题说。如果我在HTML集合中使用for循环，我会两次获得
长度。
（在Opera中）
< blockquote class =post_quotes>
>
Garrett
dhtml写道：
<！DOCTYPE HTML>
< html lang =" en">
< head>
* *< title>长度两次< / title>
< / head>
< body>
< form action =" javascript ：;" id =" form1">
* * * *< input name =" length" type =" text" />
< / form>
< script type =" text / javascript">
var f = document.forms [0] .elements，a = [];
for（p in f）{
* * a.push（''' ;''+ p +''"：''+ f [p]）;}
document.write（"< xmp>" + a.join（" ;，\ n"）+"<" +" / xmp>"）;
< / script>
< / body>
< / html>
Opera：
" 0" ：[object HTMLInputElement]，
" length" ：[object HTMLInputElement]，
" length" ：[object HTMLInputElement]，
" item" ：function item（）{[native code]}，
" namedItem" ：function namedItem（）{[native code]}，
" tags" ：function tags（）{[native code]}
但是，如果名为-length-的元素是
，则长度只会出现两次。否则，长度属性只出现一次，并且具有
" normal"表单控件数量的值。
这里可能发生什么？我怀疑
中的对象可能是具有 - length - 属性的原型，但是无法验证这一点。
hasOwnProperty总是返回false。
一个是指用户定义的对象
document.forms [0] .elements [''length'']（多个-dimensional，可以通过
的属性/方法访问），另一个是语法相同的
宿主对象（但是作为一维的immatricial变量）。
您的测试在我的Opera 9.22.8801中没有显示相同的结果;用户定义的对象似乎覆盖了主机对象。
给出像length这样的名字永远都不错用户定义的对象。
-
Bart
9月2日，5日： 50 * am，dhtml< dhtmlkitc ... @ gmail.comwrote：
dhtml写道：
标题说。如果我在HTML集合中使用for循环，我会两次获得
长度。
（在Opera中）
Garrett
使用您自己的变量/字段的预定义[保留] var名称AVOID ......
Title says it. If I use a for in loop on an HTML collection, I get
length twice.
<!DOCTYPE HTML>
<html lang="en">
<head>
<title>length twice</title>
</head>
<body>
<form action="javascript:;" id="form1">
<input name="length" type="text"/>
</form>
<script type="text/javascript">
var f = document.forms[0].elements, a=[];
for(p in f) {
a.push(''"''+p+''" : '' + f[p]);
}
document.write("<xmp>"+a.join(",\n")+"<"+"/xmp>");
</script>
</body>
</html>
Opera:
"0" : [object HTMLInputElement],
"length" : [object HTMLInputElement],
"length" : [object HTMLInputElement],
"item" : function item() { [native code] },
"namedItem" : function namedItem() { [native code] },
"tags" : function tags() { [native code] }
However, length only appears twice way if the element named -length- is
present. Otherwise, the length property only appears once, and has the
"normal" value of the number of form controls.
What could be happening here? I suspect that there may be an object in
the prototype with a - length - property, but can''t verify this.
hasOwnProperty always returns false.
Garrett
dhtml wrote:Title says it. If I use a for in loop on an HTML collection, I get
length twice.
(in Opera)
>
Garrett
dhtml wrote:
<!DOCTYPE HTML>
<html lang="en">
<head>
* *<title>length twice</title>
</head>
<body>
<form action="javascript:;" id="form1">
* * * * <input name="length" type="text"/>
</form>
<script type="text/javascript">
var f = document.forms[0].elements, a=[];
for(p in f) {
* *a.push(''"''+p+''" : '' + f[p]);}
document.write("<xmp>"+a.join(",\n")+"<"+"/xmp>");
</script>
</body>
</html>
Opera:
"0" : [object HTMLInputElement],
"length" : [object HTMLInputElement],
"length" : [object HTMLInputElement],
"item" : function item() { [native code] },
"namedItem" : function namedItem() { [native code] },
"tags" : function tags() { [native code] }
However, length only appears twice way if the element named -length- is
present. Otherwise, the length property only appears once, and has the
"normal" value of the number of form controls.
What could be happening here? I suspect that there may be an object in
the prototype with a - length - property, but can''t verify this.
hasOwnProperty always returns false.The one refers to your user-defined object
document.forms[0].elements[''length''] (multi-dimensional, accessible by
its properties/methods) and the other to the syntactically identical
host object (but as a one-dimensional immatricial variable).
Your test does not show the same result in my Opera 9.22.8801; there
the user-defined object appears to overwrite the host object.
It is never good to give names like "length" to user-defined objects.
--
Bart
On Sep 2, 5:50*am, dhtml <dhtmlkitc...@gmail.comwrote:dhtml wrote:Title says it. If I use a for in loop on an HTML collection, I get
length twice.
(in Opera)
Garrett
AVOID using predefined [reserved] var names for your own vars/fields...
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