Tokenize in JavaScript

Question

If I have a string, how can I split it into an array of words and filter out some stopwords? I only want words of length 2 or greater.

If my string is

var text = "This is a short text about StackOverflow.";

I can split it with

var words = text.split(/\W+/);

But using split(/\W+/), I get all words. I could check if the words have a length of at least 2 with

function validate(token) {
  return /\w{2,}/.test(token);
}

but I guess I could do this smarter/faster with regexp.

I also have an array var stopwords = ['has', 'have', ...] which shouldn't be allowed in the array.

Actually, if I can find a way to filter out stopwords, I could just add all letters a, b, c, ..., z to the stopwords array to only accept words with at least 2 characters.

Solution 1

I would do what you started: split by /W+/ and then validate each token (length and stopwords) in the array by using .filter().

var text = "This is a short text about StackOverflow.";
var stopwords = ['this'];

var words = text.split(/\W+/).filter(function(token) {
    token = token.toLowerCase();
    return token.length >= 2 && stopwords.indexOf(token) == -1;
});

console.log(words); // ["is", "short", "text", "about", "StackOverflow"]

You could easily tweak a regex to look for words >= 2 characters, but there's no point if you're already going to need to post-process to remove stopwords (token.length will be faster than any fancy regex you write).

Solution 2

Easy with Ramda:

var text       = "This is a short text about how StackOverflow has gas.";
var stopWords  = ['have', 'has'];
var isLongWord = R.compose(R.gt(R.__, 2), R.length);
var isGoWord   = R.compose(R.not, R.contains(R.__, stopWords));
var tokenize   = R.compose(R.filter(isGoWord), R.filter(isLongWord), R.split(' '));

tokenize(text); // ["This", "short", "text", "about", "how", "StackOverflow", "gas."]

http://bit.ly/1V5bVrP

Solution 3

What about splitting on something like this if you want to use a pure regex approach:

\W+|\b\w{1,2}\b

https://regex101.com/r/rB4cJ4/1