blocks|key|2860597|text|索引实际上是可用的，比如；|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2860598|_.sortBy([1,+4,+2,+66,+444,+9],+function(num,+index){++});|code-block|syntax|javascript|2860599|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Index is actually available like;

<pre><code>_.sortBy([1, 4, 2, 66, 444, 9], function(num, index){ });
</code></pre>

blocks|key|217856|text|您可以通过向迭代器function添加另一个参数来获取当前迭代的索引，例如|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|217857|_.each(['foo',+'bar',+'baz'],+function+(val,+i)+{
++++console.log(i+%2B+":+"+%2B+val);+//+0:+foo,+1:+bar,+2:+baz
});|code-block|syntax|javascript|217858|entityMap^0|9|8|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

You can get the index of the current iteration by adding another parameter to your iterator <code>function</code>, e.g.

<pre><code>_.each(['foo', 'bar', 'baz'], function (val, i) {
 console.log(i + ": " + val); // 0: foo, 1: bar, 2: baz
});
</code></pre>

blocks|key|217901|text|如果您更愿意转换数组，那么下划线的map函数的iterator参数也会作为第二个参数传递给索引。所以：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|217902|_.map([1,+4,+2,+66,+444,+9],+function(value,+index){+return+index+%2B+':'+%2B+value;+});|code-block|syntax|javascript|217903|..。返回：|217904|["0:1",+"1:4",+"2:2",+"3:66",+"4:444",+"5:9"]|217905|entityMap^0|H|3|N|8|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]|$9|T|A|U|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|V|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|W|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|X|8|@]|D|@]|E|$I|J]]|$1|O|3|-4|5|6|7|Y|8|@]|D|@]|E|$]]]|P|$]]

If you'd rather transform your array, then the <code>iterator</code> parameter of underscore's <code>map</code> function is also passed the index as a second argument. So:

<pre><code>_.map([1, 4, 2, 66, 444, 9], function(value, index){ return index + ':' + value; });
</code></pre>

... returns:

<pre><code>["0:1", "1:4", "2:2", "3:66", "4:444", "5:9"]
</code></pre>

blocks|key|217843|text|使用3个参数(element,+index,+list)调用_.each的迭代器。所以，是的，对于_.each，你可以得到索引。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|217844|您可以在sortBy中执行相同的操作|217845|entityMap^0|6|M|U|6|1D|6|0|0^^$0|@$1|2|3|4|5|6|7|J|8|@$9|K|A|L|B|C]|$9|M|A|N|B|C]|$9|O|A|P|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Q|8|@]|D|@]|E|$]]|$1|H|3|-4|5|6|7|R|8|@]|D|@]|E|$]]]|I|$]]

The iterator of <code>_.each</code> is called with 3 parameters <code>(element, index, list)</code>. So yes, for <code>_.each</code> you cab get the index.

You can do the same in sortBy

blocks|key|212874|text|我认为值得一提的是下划线的_.each()在内部是如何工作的。_.each(+list，iteratee)检查传递的列表是数组对象还是对象。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|212875|在列表是数组的情况下，iteratee参数将是列表元素和索引，如下例所示：|212876|var+a+=+['I',+'like',+'pancakes',+'a',+'lot',+'.'];
_.each(+a,+function(v,+k)+{+console.log(+k+%2B+"+"+%2B+v);+});

0+I
1+like
2+pancakes
3+a
4+lot
5+.|code-block|syntax|javascript|212877|另一方面，如果list参数是一个对象，则iteratee将接受一个list元素和一个键：|212878|var+o+=+{name:+'mike',+lastname:+'doe',+age:+21};
_.each(+o,+function(v,+k)+{+console.log(+k+%2B+"+"+%2B+v);+});

name+mike
lastname+doe
age+21|212879|以下是Underscore.js+1.8.3中的_.each()代码以供参考|212880|_.each+=+_.forEach+=+function(obj,+iteratee,+context)+{
+++iteratee+=+optimizeCb(iteratee,+context);
+++var+i,+length;
+++if+(isArrayLike(obj))+{
++++++for+(i+=+0,+length+=+obj.length;+i+<+length;+i%2B%2B)+{
+++++++++iteratee(obj[i],+i,+obj);
++++++}
+++}+else+{
++++++var+keys+=+_.keys(obj);
++++++for+(i+=+0,+length+=+keys.length;+i+<+length;+i%2B%2B)+{
+++++++++iteratee(obj[keys[i]],+keys[i],+obj);
++++++}
+++}
+++return+obj;
};|212881|entityMap^0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|T|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|V|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|W|8|@]|9|@]|A|$G|H]]|$1|M|3|N|5|6|7|X|8|@]|9|@]|A|$]]|$1|O|3|P|5|F|7|Y|8|@]|9|@]|A|$G|H]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

I think it's worth mentioning how the Underscore's _.each() works internally. The _.each(list, iteratee) checks if the passed list is an array object, or an object.

In the case that the list is an array, iteratee arguments will be a list element and index as in the following example:

<pre><code>var a = ['I', 'like', 'pancakes', 'a', 'lot', '.'];
_.each( a, function(v, k) { console.log( k + " " + v); });

0 I
1 like
2 pancakes
3 a
4 lot
5 .
</code></pre>

On the other hand, if the list argument is an object the iteratee will take a list element and a key:

<pre><code>var o = {name: 'mike', lastname: 'doe', age: 21};
_.each( o, function(v, k) { console.log( k + " " + v); });

name mike
lastname doe
age 21
</code></pre>

For reference this is the _.each() code from Underscore.js 1.8.3

<pre><code>_.each = _.forEach = function(obj, iteratee, context) {
 iteratee = optimizeCb(iteratee, context);
 var i, length;
 if (isArrayLike(obj)) {
 for (i = 0, length = obj.length; i &lt; length; i++) {
 iteratee(obj[i], i, obj);
 }
 } else {
 var keys = _.keys(obj);
 for (i = 0, length = keys.length; i &lt; length; i++) {
 iteratee(obj[keys[i]], keys[i], obj);
 }
 }
 return obj;
};
</code></pre>

blocks|key|212841|text|更广泛地说，在大多数情况下，下划线函数将列表和参数作为前两个参数，将列表索引作为迭代器的倒数第二个参数提供访问。当涉及到两个下划线函数_.reduce和_.reduceRight时，这是一个重要的区别，这两个函数以'memo‘作为第三个参数--在这两个函数中，索引将不是第二个参数，而是第三个参数：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|212842|var+destination+=+(function()+{
++++var+fields+=+['_333st',+'offroad',+'fbi'];
++++return+_.reduce(waybillInfo.destination.split(','),+function(destination,+segment,+index)+{
++++++++destination[fields[index]]+=+segment;
++++++++return+destination;
++++},+{});
})();

console.log(destination);++++++++++++
/*
_333st:+"NYARFTW++TX"
fbi:+"FTWUP"
offroad:+"UP"

The+following+is+better+of+course+but+not+demonstrate+my+point:
var+destination+=+_.object(['_333st',+'offroad',+'fbi'],+waybillInfo.destination.split(','));
*/|code-block|syntax|javascript|212843|因此，如果您愿意，可以使用下划线本身获取索引：_.last(_.initial(arguments))。一个可能的例外(我还没有尝试过)是_.map，因为它可以接受对象而不是列表：“如果list是一个JavaScript对象，迭代器的参数将是(value，key，list)。”--请参阅：http://underscorejs.org/#map|offset|length|style|CODE|212844|entityMap|0|LINK|mutability|MUTABLE|url|http://underscorejs.org/#map^0|0|0|N|S|41|S|0|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|W|8|@$I|X|J|Y|K|L]]|9|@$I|Z|J|10|1|11]]|A|$]]|$1|M|3|-4|5|6|7|12|8|@]|9|@]|A|$]]]|N|$O|$5|P|Q|R|A|$S|T]]]]

More generally, under most circumstances, underscore functions that take a list and argument as the first two arguments, provide access to the list index as the next to last argument to the iterator. This is an important distinction when it comes to the two underscore functions, _.reduce and _.reduceRight, that take 'memo' as their third argument -- in the case of these two the index will not be the second argument, but the third:

<pre><code>var destination = (function() {
 var fields = ['_333st', 'offroad', 'fbi'];
 return _.reduce(waybillInfo.destination.split(','), function(destination, segment, index) {
 destination[fields[index]] = segment;
 return destination;
 }, {});
})();

console.log(destination); 
/*
_333st: "NYARFTW TX"
fbi: "FTWUP"
offroad: "UP"

The following is better of course but not demonstrate my point:
var destination = _.object(['_333st', 'offroad', 'fbi'], waybillInfo.destination.split(','));
*/
</code></pre>

So if you wanted you could get the index using underscore itself: <code>_.last(_.initial(arguments))</code>. A possible exception (I haven't tried) is _.map, as it can take an object instead of a list: "If list is a JavaScript object, iterator's arguments will be (value, key, list)." -- see: <a href="http://underscorejs.org/#map" rel="nofollow">http://underscorejs.org/#map</a>

blocks|key|215916|text|当可用时，我相信大多数lodash数组函数都会显示迭代。但是排序实际上并不是以同样的方式进行迭代:当您对数字66进行排序时，直到数组中的第四项完成，您才会处理它。自定义排序函数将对数组进行多次循环，将相邻的数字向前或向后轻推，直到所有内容都放在适当的位置。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|215917|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

When available, I believe that most lodash array functions will show the iteration. But sorting isn't really an iteration in the same way: when you're on the number 66, you aren't processing the fourth item in the array until it's finished. A custom sort function will loop through an array a number of times, nudging adjacent numbers forward or backward, until the everything is in its proper place.

I'm using the JS library <a href="http://underscorejs.org" rel="noreferrer">Underscore</a> and in particular using the <a href="http://underscorejs.org/#each" rel="noreferrer"><code>_.each</code></a> and <a href="http://underscorejs.org/#sortBy" rel="noreferrer"><code>_.sortby</code></a> library calls. I'm wondering if there's any possible way to get the index of the value within the iterator delegate

<pre><code>_.sortBy([1, 4, 2, 66, 444, 9], function(num){ 
 /*It'd be great to have access to the index in here */
 return Math.sin(num); 
});
</code></pre>

Is it possible to get the index you're sorting over in Underscore.js?

我正在使用JS库，特别是使用和库调用。我想知道是否有任何可能的方法来获得迭代器委托中的值的索引_.sortBy([1, 4, 2, 66, 444, 9], function(num){     /*It'd be great to have access to the index in here */    return Math.sin(num); });

问是否可以在Underscore.js中获得要排序的索引？
EN

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问是否可以在Underscore.js中获得要排序的索引？EN

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问是否可以在Underscore.js中获得要排序的索引？
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