Javascript MongoDB - 不明白如何使用游标循环遍历集合
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MongoDB - dont understand how to loop through collections with a cursor
提问by Genadinik
advertisers = db.dbname.find( 'my query which returns things correctly' );
I realize now that it returns a cursor to the list of collections.
我现在意识到它返回一个指向集合列表的游标。
But I am not sure how to loop through them and get each collection.
但我不确定如何遍历它们并获取每个集合。
I want to try something like this:
我想尝试这样的事情：
advertisers.each(function(err, advertiser) {
console.log(advertiser);
});
But that does not work. But I didn't see from searching online how to make it actually work with simple JavaScript.
但这不起作用。但是我没有从网上搜索中看到如何使它与简单的 JavaScript 一起工作。
Then I have this code:
然后我有这个代码：
var item;
if ( advertisers != null )
{
while(advertisers.hasNext())
{
item = advertisers.next();
}
}
and it gives this error: SyntaxError: syntax error (shell):1
它给出了这个错误： SyntaxError: syntax error (shell):1
Help much appreciated!
非常感谢帮助！
Thanks!
谢谢！
回答by Justin Thomas
The quick and dirty way is:
快速而肮脏的方法是：
var item;
var items = db.test.find();
while(items.hasNext()) {
item = items.next();
/* Do something with item */
}
There is also the more functional:
还有更实用的：
items.forEach(function(item) {
/* do something */
});
回答by Neno
One more way to loop through collections is using toArray cursor's method:
循环遍历集合的另一种方法是使用 toArray 游标的方法：
var results = db.getCollection('posts').find({}).toArray();
for(var i = 0; i <= results.length -1; i++)
{
print("Author is:" + results[i].Author);
}回答by LuisCarlos Rodriguez
Since you are not showing the stack then I assume your problem is the parameter you are passing to the find function, this parameter has to be a JavaScript object, therefore:
由于您没有显示堆栈，因此我认为您的问题是您传递给 find 函数的参数，该参数必须是一个 JavaScript 对象，因此：
var query = {
key: 'my query which returns things correctly'
}
advertisers = db.dbname.find(query);
advertisers.each (function(err, doc){
//.... error code not included.....
console.log(doc);
});
