103

Is there an equivalent for ruby's array[n..m] in JavaScript?

For example:

>> a = ['a','b','c','d','e','f','g']
>> a[0..2]
=> ['a','b','c']
A-Sharabiani
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shdev
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    yes, coffeescript! [New-and-improved range, slice, splice and loop syntax](https://github.com/jashkenas/coffee-script/issues/835). – Lance May 18 '11 at 23:02

4 Answers4

179

Use the array.slice(begin [, end]) function.

var a = ['a','b','c','d','e','f','g'];
var sliced = a.slice(0, 3); //will contain ['a', 'b', 'c']

The last index is non-inclusive; to mimic ruby's behavior you have to increment the end value. So I guess slice behaves more like a[m...n] in ruby.

Nicholas Hamilton
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Vivin Paliath
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22

The second argument in slice is optional, too:

var fruits = ['apple','banana','peach','plum','pear'];
var slice1 = fruits.slice(1, 3);  //banana, peach
var slice2 = fruits.slice(3);  //plum, pear

You can also pass a negative number, which selects from the end of the array:

var slice3 = fruits.slice(-3);  //peach, plum, pear

Here's the W3 Schools reference link.

Aljaž Medič
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David Hoerster
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    How about linking to Mozilla's javascript reference, which is far more informative and much better written than the W3 schools site (which has nothing to do with the W3C)? https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array/slice – Bobby Jack Aug 26 '10 at 23:50
10

a.slice(0, 3) Would be the equivalent of your function in your example.

https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Array/slice

Robert
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    actually it would be `a.slice(0, 3)`. slice in JavaScript doesn't included the end index. – Anurag Aug 26 '10 at 23:15
4

Ruby and Javascript both have a slice method, but watch out that the second argument to slice in Ruby is the length, but in JavaScript it is the index of the last element:

var shortArray = array.slice(start, end);
Douglas
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