检查 Javascript 数组中是否存在属性值为“x”的对象
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Check whether an object with property value 'x' exists in an array in Javascript
提问by JVG
I have a lot of objects that I'm trying to filter out duplicates from. When an object has a property, IMAGEURLwhich is present in another object, I want to ignore this object and move on.
我有很多对象，我试图从中过滤掉重复项。当一个对象具有IMAGEURL另一个对象中存在的属性时，我想忽略这个对象并继续前进。
I'm using nodeJSfor this so if there's a library I can use to make it easier let me know.
我正在使用nodeJS它，所以如果有一个我可以用来使它更容易的库，请告诉我。
I've done similar implementations before with checking string values in arrays, doing something like:
我之前做过类似的实现，检查数组中的字符串值，执行如下操作：
var arr = ['foo', 'bar'];
if(arr.indexOf('foo') == -1){
arr.push('foo')
}
But this won't work for objects, as best I can tell. What are my options here? To put it more simply:
但这不适用于对象，据我所知。我在这里有哪些选择？更简单地说：
var obj1 = {IMAGEURL: 'http://whatever.com/1'};
var obj2 = {IMAGEURL: 'http://whatever.com/2'};
var obj3 = {IMAGEURL: 'http://whatever.com/1'};
var arr = [obj1, obj2, obj3];
var uniqueArr = [];
for (var i = 0; i<arr.length; i++){
// For all the iterations of 'uniqueArr', if uniqueArr[interation].IMAGEURL == arr[i].IMAGEURL, don't add arr[i] to uniqueArr
}
How can I do this?
我怎样才能做到这一点？
回答by SheetJS
You can just use an inner loop (keeping track of whether we've seen the loop by using a seenvariable -- you can actually use labels here, but I find the variable method to be easier to read):
你可以只使用一个内部循环（通过使用seen变量来跟踪我们是否已经看到了循环——你实际上可以在这里使用标签，但我发现变量方法更容易阅读）：
for (var i = 0; i<arr.length; i++){
var seen = false;
for(var j = 0; j != uniqueArr.length; ++j) {
if(uniqueArr[j].IMAGEURL == arr[i].IMAGEURL) seen = true;
}
if(!seen) uniqueArr.push(arr[i]);
}
回答by bfavaretto
Here is a concise way:
这是一个简洁的方法：
var uniqueArr = arr.filter(function(obj){
if(obj.IMAGEURL in this) return false;
return this[obj.IMAGEURL] = true;
}, {});
Note: this is concise, but orders of magnitude slowerthan Nirk's answer.
注意：这很简洁，但比Nirk's answer慢几个数量级。
See also: http://monkeyandcrow.com/blog/why_javascripts_filter_is_slow/
另见：http: //monkeyandcrow.com/blog/why_javascripts_filter_is_slow/
