Combination of valid word from a dictionary

script.js

var dic = require('./dic.json');
const stringToUse = "restaurant";
const arr = combinations(stringToUse);
const result = arr.filter(str => str.length> 1 && !!dic[str]).join(' ')
console.log(result);

// dictionary available at https://raw.githubusercontent.com/matthewreagan/WebstersEnglishDictionary/master/dictionary_compact.json

// https://codereview.stackexchange.com/a/7025/121772
function combinations(str) {
    var fn = function(active, rest, a) {
        if (!active && !rest)
            return;
        if (!rest) {
            a.push(active);
        } else {
            fn(active + rest[0], rest.slice(1), a);
            fn(active, rest.slice(1), a);
        }
        return a;
    }
    return fn("", str, []);
}