multiline_regexps.js

(function() {
  var s = "prefix arg1\narg2",
      expected_capture = "arg1\narg2",
      regexps = [
        /prefix\s+(.*)$/, // base
        /prefix\s+(.*)$/m, /prefix\s+(.*)$/g, /prefix\s+(.*)$/mg,
        
        /prefix\s([\s\S]*)$/, // base
        /prefix\s([\s\S]*)$/m, /prefix\s([\s\S]*)$/g, /prefix\s([\s\S]*)$/mg
      ];
  
  for (var i = 0, len = regexps.length; i < len; i++) {
    var regexp = regexps[i],
        match = s.match(regexp);
    if (!match) {
      console.error('RegExp %o does not match %o', regexp, s);
      continue;
    }
    
    var capture = match[1];
    if (expected_capture == capture) {
      console.log('RegExp %o successfully captures %o from %o', regexp, match[1], s);
    } else {
      console.error('RegExp %o captures wrong args %o from %o', regexp, match[1], s);
    }
  }
})();