javascript - Learn about regular expressions? -

in answer 1 of questions, had posted:

// replace easier work delimiter str.replace(/(;)(?![";"])/g, '|')  // or split it, skip on results ; var strarr = str.split(/(;)(?![";"])/); (s in strarr) {     if (strarr[s] !== ";") {         // strarr[s]         console.log(strarr[s]);     } } 

i'm lost @ /(;)(?![";"])/. looks bunch of random symbols me :( .

where can learn more regular expression syntax?

there various resources:

• mdc
• the specification (but that's going hard going)
• javascript kit's intro , reference
• evolt's regular expressions in javascript

regarding actual expression, / characters mark beginning , end of regular expression literal (like quotes string, although ending / may followed flags), , then:

     +------------- 1      |+------------ 2      ||+----------- 3      ||| +--------- 4      ||| |      ||| |      ||| | +------- 5      ||| | | +----- 6      ||| | | | +--- 7      ||| | | | |+-- 8      |||/ \|/ \||     /(;)(?![";"])/

1. ( starts capture group in case (because ( isn't followed ?, =, or ! change does)
2. ; literal, matches semicolon
3. ) ends capture group
4. (?! starts "negative lookahead" overall expression matches if what's inside parentheses isn't found after semicolon
5. [ begins character class, matches characters within it
6. ";" characters within character class. (the second " redundant.) character class contains contains ; , ".
7. ] ends character class
8. ) ends negative lookahead started in #4

so in all, match (and capture) semicolon provided it's not followed quote or semicolon. can't see particular reason capturing semicolon, perhaps there reason in context of question recommended.