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Fix reduce() so that if you don't pass in an initial value, the first item in the collection is used

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This commit is contained in:
Elliot Winkler
2010-10-31 18:51:30 -06:00
parent 31efd854f8
commit c21e7b24c6
2 changed files with 11 additions and 2 deletions
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3
test/collections.js
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@@ -65,6 +65,9 @@ $(document).ready(function() {
sum = _([1, 2, 3]).reduce(function(sum, num){ return sum + num; }, 0);
equals(sum, 6, 'OO-style reduce');
var sum = _.reduce([1, 2, 3], function(sum, num){ return sum + num; });
equals(sum, 6, 'default initial value');
});
test('collections: reduceRight', function() {

10
underscore.js
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@@ -94,10 +94,16 @@
_.reduce = _.foldl = _.inject = function(obj, iterator, memo, context) {
if (nativeReduce && obj.reduce === nativeReduce) {
if (context) iterator = _.bind(iterator, context);
return obj.reduce(iterator, memo);
var args = [iterator];
if (memo !== undefined) args.push(memo);
return obj.reduce.apply(obj, args);
}
each(obj, function(value, index, list) {
memo = iterator.call(context, memo, value, index, list);
if (memo === undefined && index == 0) {
memo = value;
} else {
memo = iterator.call(context, memo, value, index, list);
}
});
return memo;
};