RegEx for Some, Tiny American Flags for Others!

Last evening I had a moment and tried the Coderbyte challenge "when given a string of single letters, plusses, and equals signs, return true only if every letter has a plus on both sides". I came up with a four part if statement reliant on regexes.

function SimpleSymbols(str) {
  if (/(\+\w\+)+/g.test(str) && !/^\w/g.test(str) && !/=\w/g.test(str) && !/\w(?!\+)/g.test(str)) 
  {return true;}
  else {return false;}
}

In English, that's if there is a plus on either side of a letter, and if there is no letter at the start of the string, and if there is no letter with an equals sign immediately in front of it, and if there is no letter that is not followed by a plus sign... Then true.

Ben, who does JS for a living, gave me the learning that if there's more than one regex, it's probably not ideal... "There's so many edge cases". Makes sense. So, later, the Coderbyte challenge appears, "when given a string of lowercase letters, if there is an a followed by a b three spots later, return true". And I'm like, "I'll use a for loop, like we were talking about last night!"( Read more... )

More Regex Complications!

Here's one I thought would be simple, which wasn't. The problem is, "return a count of all the vowels (not y) in a string." I thought I'd use regex.exec to capture an array of vowels and find the length of the array... But it only ever returned length 2. I see in the Mozilla Developer Network info page that RexExp.length is 2, but I don't know why I'm getting that here. Can someone troubleshoot?

function VowelCount(str) { 
  var re = /([aeiou])/ig;
  var arr = re.exec(str);
  console.log(arr);
  return arr.length; 
}

console.log(VowelCount('moooo'));

So I pivoted to for loops and came up with this,

function VowelCount(str) { 
  var re = /[aeiou]/i;
  var count = 0;
  for (var i = 0; i < str.length; i++) {
    if (re.test(str.charAt(i))) {
      count += 1;
      console.log(i);
  }
  return count; 
}

This also took some troubleshooting, since the count was wrong when I was using the 'g' flag in the regex. I'm also not sure why that was. Other people I looked at also had mangled looking answers, though of course Matt Larsh has something good,

function VowelCount(str) { 
  var vowels = str.match(/[aeiou]/g);
  return vowels.length;
}

Looks like I need to bone up on str.match.