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Add _.chunk to Array functions. #1919

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Add _.chunk to Array functions. #1919

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e917a18
Add _.decompose to Array functions.
Oct 7, 2014
db7f405
Merge remote-tracking branch 'upstream/master'
Nov 4, 2014
750f22c
Add _.chunk to Array functions.
Nov 5, 2014
dbc7375
merge chunk to master
Nov 5, 2014
e3035ba
fix _.chunk function
Nov 6, 2014
63652f6
fix _.chunk function
Nov 6, 2014
a59a6f9
remove _.decompose from array functions
Nov 7, 2014
7d4034c
Do not return original array if chunkin in more then array size parts
Nov 17, 2014
ce3a67a
Do not return original array if chunkin in more then array size parts
Nov 17, 2014
0c6d140
spaces clean up
Jan 20, 2015
185abf6
chunk(): set default parts to 1
Apr 13, 2015
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16 changes: 15 additions & 1 deletion test/arrays.js
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Original file line number Diff line number Diff line change
Expand Up @@ -418,5 +418,19 @@
deepEqual(_.range(12, 7, -2), [12, 10, 8], 'range with three arguments a & b & c, a > b, c < 0 generates an array of elements a,a-c,a-2c and ends with the number not less than b');
deepEqual(_.range(0, -10, -1), [0, -1, -2, -3, -4, -5, -6, -7, -8, -9], 'final example in the Python docs');
});


test('chunk', function() {
deepEqual(_.chunk([], 2), [], 'chunk for empty array returns an empty array');
deepEqual(_.chunk(null, 2), [], 'chunk for null returns an empty array');

deepEqual(_.chunk([1, 2, 3], 0), [], 'chunk into parts of 0 elements returns an empty array');
deepEqual(_.chunk([1, 2, 3], -1), [], 'chunk into parts of negative amount of elements returns an empty array');

deepEqual(_.chunk([1, 2, 3], 3), [[1, 2, 3]], 'chunk into parts of current array length elements returns the original array');
deepEqual(_.chunk([1, 2, 3], 5), [[1, 2, 3]], 'chunk into parts of more then current array length elements returns the original array');

deepEqual(_.chunk([10, 20, 30, 40, 50, 60, 70], 2), [[10, 20], [30, 40], [50, 60], [70]], 'chunk into parts of less then current array length elements');
deepEqual(_.chunk([10, 20, 30, 40, 50, 60, 70], 3), [[10, 20, 30], [40, 50, 60], [70]], 'chunk into parts of less then current array length elements');
});

}());
14 changes: 14 additions & 0 deletions underscore.js
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Expand Up @@ -646,6 +646,20 @@

return range;
};

// Split an **array** into several arrays containing **count** or less elements
// of initial array
_.chunk = function(array, count) {
var result = [];
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hmm, I wonder if it's faster to compute the length new Array(Math.ceil(array.length / count)) - feel free not to bother with it


if (array == null || count <= 0) return [];

for (var i = 0, lng = array.length; i < lng;) {
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Mind using length instead of lng?

result.push(array.slice(i, i += count));
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We should use slice.call(array, i, i+= count) to sidestep overwritten Array#slice and open this up to array-likes.

}
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I would probably write line 655-659 as

var i = 0, length = array && array.length, j = 0;
while (i < length && count >= 0) {
     if (i % count) result[j++] = [];
     result[j].push(array[i]);
}

(untested). I would be curious to see some benchmarks


return result;
};

// Function (ahem) Functions
// ------------------
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