Map a phone number to potential words. This part produces all possible combinations.

combos.js

var digits = {2: ['a', 'b', 'c'], 3: ['d', 'e', 'f'], 4: ['g','h','i'], 5: ['j','k','l'], 6: ['m','n','o'], 7:['p', 'q', 'r', 's'], 8: ['t','u','v'], 9: ['x','y','z']};

function crossProduct(sets) {
    var r = sets.reduce((p,c) => {
        return p.map(x => {
            return c.map(y => {
                return x.concat(y);
            })
        }).reduce((prev,cur) => { return prev.concat(cur) },[])
    }, [[]]).map(s => s.join(''));
    return r;
}

function getSets(number) {
    return number.split('').map(n => (digits[n]) ? digits[n] : [])
                           .filter(s => s.length);
}

module.exports = {
    getCombos: number => {
        var sets = getSets(number);
        return crossProduct(sets);
    }
};

numberAnalyzer.js

// usage: node numberAnalyzer.js 4243
// output: [ 'gage', 'ibid' ]

var digitConverter = require('./combos');
var natural = require("natural");
var fs = require("fs");

// assumes that you have a '\n'-separated english dictionary file.
// which you can get from a number of places...
const dictionary = "dictionary/en_wordlist.txt";
const number = process.argv[2];
var trie = new natural.Trie(false);

var loadDictionary = new Promise((resolve, reject) => {
    fs.readFile(dictionary, {"encoding":"ascii"}, (err, data) => {
        if (err) reject(err);
        else resolve(data); 
    });
});
loadDictionary.then(data => {
    var words = data.split("\n").map(w => w.trim())
                                .filter(w => w.length <= 10);
    trie.addStrings(words);

    var combos = digitConverter.getCombos(number);
    var words = combos.filter(w => trie.contains(w));
    if (words.length) {
        console.log(words);
    } else {
        console.log('no matches.');
    }
}).catch(err => {
    console.err(err);
});

node numberAnalyzer.js 3878
[ 'dust' ]