Question

I am in need for a regex in Javascript. I have a string:

'*window.some1.some\.2.(a.b + ")" ? cc\.c : d.n [a.b, cc\.c]).some\.3.(this.o.p ? ".mike." [ff\.]).some5'

I want to split this string by periods such that I get an array:

[
    '*window',
    'some1',
    'some\.2',   //ignore the . because it's escaped
    '(a.b ? cc\.c : d.n [a.b, cc\.c])',  //ignore everything inside ()
    'some\.3',
    '(this.o.p ? ".mike." [ff\.])',
    'some5'
]

What regex will do this?

Answer 1

var string = '*window.some1.some\\.2.(a.b + ")" ? cc\\.c : d.n [a.b, cc\\.c]).some\\.3.(this.o.p ? ".mike." [ff\\.]).some5';
var pattern = /(?:\((?:(['"])\)\1|[^)]+?)+\)+|\\\.|[^.]+?)+/g;
var result = string.match(pattern);
result = Array.apply(null, result); //Convert RegExp match to an Array

Fiddle: http://jsfiddle.net/66Zfh/3/
Explanation of the RegExp. Match a consecutive set of characters, satisfying:

/             Start of RegExp literal
(?:            Create a group without reference (example: say, group A)
   \(          `(` character
   (?:         Create a group without reference (example: say, group B)
      (['"])     ONE `'` OR `"`, group 1, referable through `\1` (inside RE)
      \)         `)` character
      \1         The character as matched at group 1, either `'` or `"`
     |          OR
      [^)]+?     Any non-`)` character, at least once (see below)
   )+          End of group (B). Let this group occur at least once
  |           OR
   \\\.        `\.` (escaped backslash and dot, because they're special chars)
  |           OR
   [^.]+?      Any non-`.` character, at least once (see below)
)+            End of group (A). Let this group occur at least once
/g           "End of RegExp, global flag"
        /*Summary: Match everything which is not satisfying the split-by-dot
                 condition as specified by the OP*/

There’s a difference between + and +?. A single plus attempts to match as much characters as possible, while a +? matches only these characters which are necessary to get the RegExp match. Example: 123 using \d+? > 1 and \d+ > 123.

The String.match method performs a global match, because of the /g, global flag. The match function with the g flag returns an array consisting of all matches subsequences.

When the g flag is omitted, only the first match will be selected. The array will then consist of the following elements:

Index 0: <Whole match>
Index 1: <Group 1>