javascript：获取所有对象参数
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javascript: get all object parameters
提问by Sorin Buturugeanu
I have a JS object with a variable number of parameters. Is there a way to see what parameters have been passed this particular time?
我有一个带有可变数量参数的 JS 对象。有没有办法查看这个特定时间传递了哪些参数？
The example:
这个例子：
function getElement() {
var scope = document;
this.by = function(data){
if (data.id) scope = scope.getElementById(data.id);
if (data.tag) scope = scope.getElementsByTagName(data.tag);
return scope;
}
}
And I run it like so
我像这样运行它
var x = new getElement();
vad div = x.by({id : "chosenID"});
gets the div with the id chosenID
获取带有 id 的 div chosenID
or
或者
var x = new getElement();
vad inputs = x.by({id : "chosenID", tag : "input"});
gets all the inputsin the div with the id chosenID;
inputs使用 id获取div 中的所有内容chosenID；
I want to know if I passed one or two parameters, and which ones.
我想知道我是否传递了一两个参数，以及哪些参数。
Thanks!
谢谢！
ps: I appreciate your time in helping me out, but please do not sugget jQuery or other JS framework as this is for learning purposes only. Much obliged, Sorin.
ps：感谢您花时间帮助我，但请不要建议使用 jQuery 或其他 JS 框架，因为这仅用于学习目的。非常感谢，索林。
回答by Marcel Korpel
Use a for … inloop to iterate over the passed object's parameters, like:
使用for … in循环遍历传递对象的参数，例如：
var prop;
for (prop in data) {
if (data.hasOwnProperty(prop)) {
// do something with data[prop]
}
}
Don't forget to check the property with hasOwnProperty.
不要忘记使用 来检查属性hasOwnProperty。
回答by Rudu
Using object iteration (key in data) and array-combining... you can return a number of elements... although the object iteration is rendered pretty useless by by the switch statement.
使用对象迭代 ( key in data) 和数组组合……您可以返回许多元素……尽管 switch 语句使对象迭代变得毫无用处。
function getElement() {
var scope = document;
this.by = function(data){
var key;
var ret=[];
for (key in data) {
if(data.hasOwnProperty(key)) {
switch(key) {
case "id":
ret=ret.concat(scope.getElementById(data[key]));
break;
case "tag":
ret=ret.concat(scope.getElementsByTagName(data[key]));
break;
default:
throw new Error("Unknown property "+key);
}
}
}
return ret;
};
}
回答by Rudu
There are lots of good generalanswers, however consider this:
有很多很好的通用答案，但是请考虑一下：
So, instead, I will cover some specific cases. First off, I generally start with:
因此，相反，我将介绍一些特定情况。首先，我通常从以下几点开始：
function f (x) {
x = x || {} // so f() will be accepted as per f({})
...
}
This also sets up the context for the following.
这也为以下内容设置了上下文。
My normal approach is just to check for a truth-y value. A true value means "supplied". However this has the disadvantage of not treating 0 or '' as "supplied".
我通常的方法只是检查真值。真值意味着“提供”。然而，这具有不将 0 或 '' 视为“已提供”的缺点。
if (x.id) {
// x.id is any truth-y
}
If 0 is an accepted input then I widen the check so that non-undefinedvalues are considered "supplied". An unset property always defaults to undefined. (This method will accept all truth-y values and false-y values such as 0, "", and null).
如果 0 是可接受的输入，那么我会扩大检查范围，以便将非undefined值视为“已提供”。未设置的属性始终默认为undefined。（此方法将接受所有真 y 值和假 y 值，例如 0、"" 和null）。
if (x.id !== undefined) {
// x.id is all truth-y and all-but-undefined false-y
}
If undefinedis an accepted input (which I would strongly argue against), then the check can be based on hasOwnProperty. This has the dis-advantage of not checking up the [[prototype]]chain.
如果undefined是可接受的输入（我强烈反对），则检查可以基于hasOwnProperty. 这具有不检查[[prototype]]链的缺点。
if (x.hasOwnProperty("id")) {
// x.id set to something, including undefined
}
The for(..in..)construct can also be used to iterate over the properties in an object (including properties in the [[prototype]]unless they are specially hidden). However, for the general case of dealing with input (e.g. not creating a JSON library), I find it is simple and clean just to deal with the properties on the input object(s) in one of the methods described above.
该for(..in..)构造还可用于迭代对象中的属性（包括 中的属性，[[prototype]]除非它们被特别隐藏）。但是，对于处理输入的一般情况（例如，不创建 JSON 库），我发现仅用上述方法之一处理输入对象上的属性就很简单。
