Strange string split behavior in Javascript

Question

When I run

'{{123}}'.split(/(\{\{)|(\}\})/g, -1)

I expect

["", "123", ""]

But it shows

["", "{{", undefined, "123", undefined, "}}", ""]

Why?? Is there anything wrong?

Why have you passed a negative limit?

David Thomas
– David Thomas

2012-09-16 12:59:26 +00:00
Commented Sep 16, 2012 at 12:59 — David Thomas
– David Thomas, Commented Sep 16, 2012 at 12:59

xdazz · Accepted Answer · 2012-09-16 13:51:32Z

2

Use:

'{{123}}'.split(/\{\{|\}\}/)

You don't need to catch group when using .split

edited Sep 16, 2012 at 13:51

answered Sep 16, 2012 at 12:58

xdazz

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1 Comment

pimvdb Over a year ago

You don't need the global flag, and -1 as a limit is not very useful either I think.

clyfish · Accepted Answer · 2012-09-16 13:22:18Z

1

http://es5.github.com/#x15.5.4.14

If separator is a regular expression that contains capturing parentheses, then each time separator is matched the results (including any undefined results) of the capturing parentheses are spliced into the output array. For example,

"A<B>bold</B>and<CODE>coded</CODE>".split(/<(\/)?([^<>]+)>/)

evaluates to the array

["A", undefined, "B", "bold", "/", "B", "and", undefined, "CODE", "coded", "/", "CODE", ""]

So, '{{123}}'.split(/(\{\{)|(\}\})/g, -1) returns

["",
"{{", undefined, // "{{" is matched, but "}}" isn't.
"123",
undefined, "}}", // "{{" isn't matched, but "}}" is matched. 
""]

edited Sep 16, 2012 at 13:22

answered Sep 16, 2012 at 13:14

clyfish

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