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I need to split the string "thisIs12MyString" to an array looking like [ "this", "Is", "12", "My", "String" ]

I've got so far as to "thisIs12MyString".split(/(?=[A-Z0-9])/) but it splits on each digit and gives the array [ "this", "Is", "1", "2", "My", "String" ]

So in words I need to split the string on upper case letter and digits that does not have an another digit in front of it.

I need to split the string "thisIs12MyString" to an array looking like [ "this", "Is", "12", "My", "String" ]

I've got so far as to "thisIs12MyString".split(/(?=[A-Z0-9])/) but it splits on each digit and gives the array [ "this", "Is", "1", "2", "My", "String" ]

So in words I need to split the string on upper case letter and digits that does not have an another digit in front of it.

• javascript
• regex

Share Improve this question Follow asked Feb 26, 2012 at 13:20 Jesper PalmJesper Palm 7,2483333 silver badges3636 bronze badges 5

• @Jesper Oh, it's actually pretty tricky, because javascript does not handle lookbehinds. – Mikulas Dite Commented Feb 26, 2012 at 13:30
• Is it important that you do this with a single regex? Why not break it down into two parts? It will probably increase readability. – davin Commented Feb 26, 2012 at 13:32
• I don't think you can do this with a lookahead or even one expression along (that said, I would not consider myself as a regex expert). One idea could be to insert a special character before each sequence of digits and split by this character too. – Felix Kling Commented Feb 26, 2012 at 13:33
• @MikulasDite Thanks for trying I got the feeling this one wasn't totally easy. Probably easier to change my naming convention. – Jesper Palm Commented Feb 26, 2012 at 13:34
• It's also quite unclear in one regex: why should 1 and 2 group together but not 1, 2 and M? what would happen with more than one upper-case letter next to another? Perhaps 2 splits is the way to go. – cmbuckley Commented Feb 26, 2012 at 13:36

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5 Answers 5

Sorted by: Reset to default 9

Are you looking for this?

"thisIs12MyString".match(/[A-Z]?[a-z]+|[0-9]+/g)

returns

["this", "Is", "12", "My", "String"]

As I said in my ment, my approach would be to insert a special character before each sequence of digits first, as a marker:

"thisIs12MyString".replace(/\d+/g, '~$&').split(/(?=[A-Z])|~/)

where ~ could be any other character, preferably a non-printable one (e.g. a control character), as it is unlikely to appear "naturally" in a string.

In that case, you could even insert the marker before each capital letter as well, and omit the lookahead, making the split very easy:

"thisIs12MyString".replace(/\d+|[A-Z]/g, '~$&').split('~')

It might or might not perform better.

In my rhino console,

js> "thisIs12MyString".replace(/([A-Z]|\d+)/g, function(x){return " "+x;}).split(/ /);
this,Is,12,My,String

another one,

js> "thisIs12MyString".split(/(?:([A-Z]+[a-z]+))/g).filter(function(a){return  a;});
this,Is,12,My,String

You can fix the JS missing of lookbehinds working on the array split using your current regex.
Quick pseudo code:

var result = [];
var digitsFlag = false;
"thisIs12MyString".split(/(?=[A-Z0-9])/).forEach(function(word) {

    if (isSingleDigit(word)) {
        if (!digitsFlag) {
            result.push(word);
        } else {
            result[result.length - 1] += word;
        }
        digitsFlag = true;
    } else {
        result.push(word);
        digitsFlag = false;
    }

});

I can't think of any ways to achieve this with a RegEx.

I think you will need to do it in code.

Please check the URL, same question different language (ruby) ->

The code is at the bottom: http://code.activestate./recipes/440698-split-string-on-capitalizeduppercase-char/

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