JavaScript code to filter out common words in a string

Question

I\'m trying to build JavaScript code that reads one string (say a sentence of English text), then outputs another string of (comma-separated) words that were \"uncommon\". S

Answer 1

The String#diff function returns a list of differences (uncommon terms). The terms can be provided as an array or a string.

You call it like: sentence.diff(terms). Below is a unit test:

var sentence = 'The dog ran to the other side of the field.';
var terms    = 'the, it is, we all, a, an, by, to, you, me, he, she, they, we, how, it, i, are, to, for, of';
// NOTE: The "terms" variable could also be an array.

(sentence.diff(terms).toString() === 'dog,ran,other,side,field')
  ? console.log('pass')
  : console.log('fail');

Below is the 'String.diff' function definition:

String.prototype.diff = function(terms){
  if (!terms) {
    return [];
  }

  if (typeof terms === 'string') {
    terms = terms.split(/,[\s]*/);
  }

  if (typeof terms !== 'object' || !Array.isArray(terms)) {
    return [];
  }

  terms = terms.map(function(term){
    return term.toLowerCase();
  });

  var words = this.split(/[\W]/).filter(function(word){
    return word.length;
  });

  return words.filter(function(word){
    return terms.indexOf(word.toLowerCase()) < 0;
  });
};