Extract variable but not function from JavaScript by Regex

Question

I am trying to extract variables (with dot notation) but not functions from a string of JavaScript using Regex. This is what I have done so far.

var regex = /([_a-zA-Z0-9\[\]]+(?:\.)?)+/g;

However, this regex will also extract JavaScript functions. For example,

var regex = /([_a-zA-Z0-9\[\]]+(?:\.)?)+/g;
console.log("a.b.c(d.e) === f".match(regex));

will output

["a.b.c", "d.e", "f"]

but I am expecting

["d.e", "f"]

Answer 1

After the end of the match, you can negative lookahead for ( , to ensure that the captured substring is not a function call. Also negative lookahead for any of the characters in the same initial character set to make sure that the backtracking from a failed function match doesn't match part of the function substring:

 var regex = /([\\w[\\]]+\\.?)+(?![.\\w[\\]]|\\s*\\()/g; console.log("abc(de) === f + q[w]e && obj[prop]()".match(regex)); 

It would probably be better to repeat groups of . followed by word characters, or [ followed by word characters and ] :

 var regex = /\\w+(?:\\.\\w+|\\[\\w+\\])+(?![([\\].])/g; console.log("abc(de) === f + q[w].e && obj[prop]()".match(regex)); 

\\w+(?:\\.\\w+|\\[\\w+\\])+(?![([\\].]) means:

• \\w+ - Word characters ( [A-Za-z0-9_]+ )
• (?:\\.\\w+|\\[\\w+\\])+ - Repeat either:
  • \\.\\w+ - A . followed by word characters, or
  • \\[\\w+\\] - [ , followed by word characters, followed by ]
• (?![([\\].]) - At the end of the pattern, negative lookahead for ( , [ , ] , and .