javascript 无法获取列表的长度
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Cannot get length of a list
提问by dotty
Hay, i have the following list
嘿，我有以下清单
var feedObjects = {
0:[
"url",
"image"
],
1:[
"url",
"image"
]
}
However when i try doing feedObjects.length it always returns null, any ideas?
但是，当我尝试执行 feedObjects.length 时，它总是返回 null，有什么想法吗？
回答by alex
You have an Object({}are the literal Objectnotation), notan Array, so there is no lengthproperty.
你有一个Object（{}有文字Object符号），不是一个Array，所以没有length财产。
You will need to iterate over it with for ( in ), except this guarantees no ordering of the properties, unlike an Array(though in practice they generally come in the order defined).
您将需要使用 迭代它for ( in )，除了这保证没有属性的排序，与 不同Array（尽管实际上它们通常按定义的顺序出现）。
Better still, swap { }with [ ]and use a real Array(well as close as JavaScript's arrays are to real ones).
更妙的是，换{ }用[ ]和使用一个真正的Array（以及靠近JavaScript的数组是以假乱真）。
回答by Tim Rogers
You have declared an associative array, not an indexed array. Try this
您已声明关联数组，而不是索引数组。试试这个
var feedObjects = [
[
"url",
"image"
],
[
"url",
"image"
]
];
回答by kennebec
Your object doesn't have a length property or method-
您的对象没有长度属性或方法-
you need to count its members.
你需要计算它的成员。
var feedObjects={
["url","image"],["url","image"]
}
function count(){
var counter= 0;
for(var p in this){
if(this.hasOwnProperty(p))++counter;
}
return counter;
}
count.call(feedObjects)
returned value: (Number)=2
返回值：(Number)=2
or define an array:
或定义一个数组：
var feedObjects=[ ["url","image"],["url","image"]];
//feedObjects.length=2;
//feedObjects.length=2;
回答by FoRever_Zambia
Object.size = function(obj) {
var size = 0, key;
for (key in obj) {
if (obj.hasOwnProperty(key)) size++;
}
return size;
};
alert(Object.size(feedObjects))
