Generate w-shingles from a string or array in JavaScript. https://en.wikipedia.org/wiki/W-shingling

shingles.js

/**
 * Make w-shingles from a source string or array.
 * @param  {string} collection The collection (array or string) to shingle.
 * @param  {string} size The shingle size (4 for 4-shingles, etc.)
 * @return {array} An array of shingles.
 */
function shingle(collection, size) {
    var shingles = [];
    for (var i=0; i<collection.length-size+1; i++) {
        shingles.push(collection.slice(i, i+size));
    }
    return shingles;
}

var testString = "a rose is a rose is a rose";
console.log(testString);
// Shingle words
console.log("Words:", shingle(testString.split(' '), 4));
// Shingle characters
console.log("Characters:", shingle(testString, 4));