My code is as follows:-

var generateTypos = function(keywords, options) {
 // Adding a function to the String Prototype that allows to
// change characters at a certain index.
// Needed, since "string"[n] is read-only
String.prototype.replaceAt=function(index, char) {
return this.substr(0, index) + char + this.substr(index+char.length);
};
// Basically a JS Implementation of
// http://web-professor.net/scripts/typo/cTypoGenerator.txt
var keyboard = {"1":["2","q"],"2":["1","q","w","3"],"3":["2","w","e","4"],"4":  ["3","e","r","5"],"5":["4","r","t","6"],"6":["5","t","y","7"],"7":["6","y","u","8"],"8":["7","u","i","9"],"9":["8","i","o","0"],"0":["9","o","p","-"],"-":["0","p"],"q":["1","2","w","a"],"w":["q","a","s","e","3","2"],"e":["w","s","d","r","4","3"],"r":["e","d","f","t","5","4"],"t":["r","f","g","y","6","5"],"y":["t","g","h","u","7","6"],"u":["y","h","j","i","8","7"],"i":["u","j","k","o","9","8"],"o":["i","k","l","p","0","9"],"p":["o","l","-","0"],"a":["z","s","w","q"],"s":["a","z","x","d","e","w"],"d":["s","x","c","f","r","e"],"f":["d","c","v","g","t","r"],"g":["f","v","b","h","y","t"],"h":["g","b","n","j","u","y"],"j":["h","n","m","k","i","u"],"k":["j","m","l","o","i"],"l":["k","p","o"],"z":["x","s","a"],"x":["z","c","d","s"],"c":["x","v","f","d"],"v":["c","b","g","f"],"b":["v","n","h","g"],"n":["b","m","j","h"],"m":["n","k","j"]},
typos = [];
// Generate a homophone object
function getHomophones() {
// German + English Homophones
var homophones = ["Aale, Ahle","Ai, Ei","Annalen, analen","aß, Aas","Bad, bat","bald, ballt","Bällen, bellen","Band, bannt","Beete, bete","bis, Biss","Block, Blog","Boot, bot","Boote, Bote","Bug, buk","Bund, bunt","Chor, Korps","Code, Kot","das, dass","dehnen, denen","erhält, erhellt","Fähre, faire","Fälle, Felle","fällt, Feld","Färse, Ferse, Verse","fast, fasst","fetter, Vetter","fiel, viel","fließt, fliehst, fliest","frisst, Frist","Fühler, Phyla","Geld, gellt","Gewand, gewandt","Grad, Grat","Graf, Graph","Halt, hallt","hallte, halte","hält, Held, hellt","Hämmer, Hemmer","hängst, Hengst","harrt, hart","hasst, hast","Häute, heute","Heer, hehr, her","Hemd, hemmt","hohl, hol","Hund, Hunt","isst, ist","kannte, Kante","konnten, Konten","Kuh, Coup","küsste, Küste","Laib, Leib","Laie, Leihe","laichen, Leichen","lasst, Last","läuten, Leuten","Lärche, Lerche","Leere, Lehre","leeren, lehren","Leerstelle, Lehrstelle","Leid, leiht","Lid, Lied","lies, ließ","liest, least","Mahl, Mal","Mähre, Märe, Meere","mahlen, malen","man, Mann","Märkte, merkte","Meer, mehr","Miene, Mine","misst, Mist","Mohr, Moor","mühten, Mythen","Mund, Munt","Nachnahme, Nachname","nahmen, Namen","packt, Pakt","pisste, Piste","rächen, Rechen","rächt, Recht","Rad, Rat","Rain, rein","Rede, Reede","Reis, reiß","reist, reißt","ruhte, Rute, Route","säen, sähen","Sämann, Seemann","Sätzen, setzen","Saite, Seite","seid, seit","schafft, Schaft","schallten, schalten","Schänke, schenke","schellte, Schelte","Schlächter, schlechter","Schlämme, schlemme","Schwälle, Schwelle","Schwämme, Schwemme","Seen, sehen","seid, seiht, seit","sie, sieh","Siegel, Sigel","Sohle, Sole","Sold, sollt","späht, spät","Stadt, statt","Städte, Stätte","Ställe, Stelle","starrt, Start","stehlen, Stelen","stiehl, Stiel, Stil","Tod, tot","Trend, trennt","Uhrzeit, Urzeit","Verband, verbannt","Verben, werben","verließ, Verlies","verwaist, verweist","Villen, Willen","Waage, vage","Waagen, wagen","Wahl, Wal","wahr, war","wahre, Ware","Waise, Weise","Wald, wallt","Wälle, Welle","Wände, Wende","Weck, weg","Wehr, wer","wehrt, Wert","weiht, weit","weis, weiß","weist, weißt","wieder, wider","wird, Wirt","Zunahme, Zuname","accept,except","acclamation,acclimation","acts,ax,axe","adolescence,adolescents","aeration,erration","aerie,airy","affect,effect","aid,aide","ail,ale","air,heir,err,ere","aisle,isle,I'll","all,awl","allowed,aloud","allude,elude","altar,alter","appose,oppose","arc,ark","are,our","ascent,assent","ate,eight","away,aweigh","aye,I,eye","bade,bayed","bail,bale","bait,bate","bald,bawled,balled","ball,bawl","band,banned","bard,barred","bare,bear","baron,barren","base,bass","based,baste","bazaar,bizarre","be,bee","beach,beech","bean,been","beat,beet","been,bin","beer,bier","bell,belle","berry,bury","berth,birth","better,bettor","bight,bite","billed,build","bird,burred","blew,blue","boar,bore,boor","board,bored","boarder,border","bode,bowed","bold,bowled","bolder,boulder,bowlder","bole,bowl","boos,booze","bough,bow","boy,buoy","braid,brayed","braise,braze,brays,braize","brake,break","breach,breech","bread,bred","brewed,brood","brews,bruise","bridal,bridle","burro,burrow","bus,buss","bused,bust","but,butt","buy,bye,by","cache,cash","callous,callus","can't,cant","cannon,canon","canter,cantor","carat,carrot,caret","caries,carries","cast,caste","cede,seed","cell,sell","cellar,seller","censor,sensor","cent,sent,scent","cents,sense,scents","cereal,serial","cession,session","chaise,chase","chalk,chock","chance,chants","chased,chaste","cheap,cheep","chews,choose","chic,sheik","choir,quire","chord,cored,cord","chute,shoot","cite,site,sight","clause,claws","click,clique","close,clothes","coal,cole","coaled,cold","coarse,course","coated,coded","cocks,cox","complement,compliment","contingence,contingents","coo,coup","coop,coupe","correspondence,correspondents","cosign,cosine","council,counsel","councilor,counselor","creak,creek","crewed,crude","crews,cruise","cue,queue","currant,current","curser,cursor","dam,damn","Dane,deign","days,daze","dear,deer","dense,dents","dependence,dependents","dew,due,do","die,dye","dire,dyer","discreet,discrete","doe,dough","does,doze,doughs","done,dun","dual,duel","ducked,duct","earn,urn","either,ether","emigrant,immigrant","eutopia,utopia","ewe,you,yew","eyed,I'd","fain,feign","faint,feint","fair,fare","fairy,ferry","fate,fete","faze,phase","feat,feet","feudal,futile","find,fined","finish,Finnish","fir,fur","flair,flare","flea,flee","flecks,flex","flew,flue","flour,flower","foaled,fold","for,four,fore","forego,forgo","foreword,forward","forth,fourth","foul,fowl","frees,frieze,freeze","friar,fryer","gage,gauge","gait,gate","gel,jell","gene,jean","gild,guild","gneiss,nice","gored,gourd","grade,grayed,greyed","grate,great","grays,greys,graze","grisly,grizzly","groan,grown","guessed,guest","guide,guyed","guise,guys","hail,hale","hair,hare","hairy,harry","hall,haul","halve,have","hangar,hanger","hay,hey","hays,haze","he'd,heed","he'll,heel,heal","hear,here","heard,herd","heated,heeded","hew,hue","hi,high","higher,hire","him,hymn","ho,hoe","hoar,whore","hoard,horde","hoarse,horse","hoes,hose","hold,holed","hole,whole","holey,wholly,holy","hostel,hostile","hour,our","idle,idol","immanent,imminent","in,inn","incidence,incidents","incite,insight","instance,instants","intense,intents","intension,intention","it's,its","jam,jamb","knave,nave","knead,need,kneed","knew,new","knight,night","knit,nit","knot,not,naught","know,no","knows,nose","lacks,lax","lade,laid","lain,lane","lair,layer","lam,lamb","laps,lapse","lay,lei","lays,laze","leach,leech","lead,led","leak,leek","lean,lien","leased,least","lends,lens","lessen,lesson","lesser,lessor","let's,lets","levee,levy","liar,lyre","lichen,liken","lickerish,licorice","lie,lye","links,lynx","lo,low","load,lode","loan,lone","loch,lock","locks,lox","loop,loupe","loos,lose","lose,loose","made,maid","mail,male","main,mane","maize,maze,Mays","mall,maul","manner,manor","marshal,martial","massed,mast","mat,matte","mean,mien","meat,mete,meet","medal,mettle,meddle,metal","might,mite","mince,mints","mind,mined","miner,minor","missed,mist","moat,mote","mood,mooed","moor,more","morning,mourning","muscle,mussel","mussed,must","naval,navel","nay,neigh","nicks,nix","none,nun","oar,ore,or","ode,owed","oh,owe","once,wants","one,won","oohs,ooze","overseas,oversees","paced,paste","packed,pact","pail,pale","pain,pane","pair,pear,pare","palate,pallet,palette","parish,perish","passed,past","patience,patients","pause,paws","peace,piece","peak,pique,peek","peal,peel","pearl,purl","pedal,petal,peddle","peer,pier","penance,pennants","per,purr","pi,pie","plain,plane","plainer,planer,planar","plait,plate","pleas,please","pole,poll","poor,pour,pore","populace,populous","praise,preys,prays","pray,prey","precedence,precedents","premier,premiere","presence,presents","pride,pried","prier,prior","pries,prize","prince,prints","principal,principle","profit,prophet","rack,wrack","raid,rayed","rail,rale","rain,rein,reign","raise,raze,rays","rap,wrap","rapt,wrapped,wrapt","re-cover,recover","re-lay,relay","read,red","read,reed","real,reel","recede,reseed","reek,wreak","residence,residents","rest,wrest","retch,wretch","rhyme,rime","right,write,rite,wright","ring,wring","ringer,wringer","rise,ryes","road,rowed,rode","roe,row","roil,royal","role,roll","roomer,rumor,rumour","root,route","rose,rows","rote,wrote","rude,rued","rues,ruse","rung,wrung","rye,wry","sail,sale","scene,seen","sea,see","seam,seem","sear,seer","seas,seize,sees","sects,sex","sew,sow,so","shake,sheik","shear,sheer","shoe,shoo","sic,sick","sics,six","side,sighed","sighs,size","sign,sine","slay,sleigh","sleight,slight","slew,slough","soar,sore","soared,sword","sold,soled","sole,soul","some,sum","son,sun","stair,stare","stake,steak","steal,steel","step,steppe","storey,story","straight,strait","suite,sweet","tacked,tact","tacks,tax","tail,tale","taper,tapir","tarry,terry","taught,taut","tea,tee","team,teem","tears,tiers","teas,tees,tease","tense,tents","than,then","there,they're,their","threw,through","throne,thrown","thyme,time","tide,tied","tier,tire","tighten,titan","to,two,too","toad,towed,toed","toe,tow","told,tolled","tracked,tract","tray,trey","udder,utter","vain,vein,vane","vale,veil","vial,vile","vice,vise","wade,weighed","wail,whale","waist,waste","wait,weight","waive,wave","waiver,waver","wale,whale","war,wore","ward,warred","ware,where,wear","warn,worn","wax,whacks","way,whey,weigh","we,wee","we'd,weed","we'll,wheel,weal,wheal","we're,weir,were","we're,whir","we've,weave","weak,week","wearer,where're","weather,whether","wet,whet","wheeled,wield","which,witch","while,wile","whiled,wild","whine,wine","whined,wined,wind","whirled,world","whit,wit","whither,wither","who's,whose","whoa,woe","wood,would","yack,yak","yaw,your,yore,you're","yoke,yolk","yore,your,you're","you'll,Yule","aahed,odd","adieu,ado","ant,aunt","aural,oral","marry,merry","rout,route","seated,seeded","shone,shown","tidal,title","trader,traitor","vary and very"];
var word_sets = homophones.map(function(x) {
return x.toLocaleLowerCase().trim().split(',');
}),
dictionary = {};
word_sets.forEach(function(set) {
set.forEach(function(word) {
dictionary[word] = set;
});
});

return dictionary;
}

// Generate wrong key typos
function wrongKeyTypos(word) {
var word = word.toLocaleLowerCase(),
typos = [],
length = word.length;

for(var i = 0; i 

new to javascript and node.js, please help me.

 Whenever I try to run the program I receive an error
 node.js:201
    throw e; // process.nextTick error, or 'error' event on first tick
          ^
 TypeError: Object  has no method 'forEach'
 at Object. (/home/chiranjit/Downloads/node-v0.10.20/typos.js:248:7)
 at Module._compile (module.js:441:26)
 at Object..js (module.js:459:10)
 at Module.load (module.js:348:32)
 at Function._load (module.js:308:12)
 at Array.0 (module.js:479:10)
 at EventEmitter._tickCallback (node.js:192:41)

I do not understand where is the Error. Please help me with the following. How to get rid of TypeError: Object has no method 'forEach'. Also placed '' after the reduce functions as suggested. But then it throws the above error.

Basically, if you look at the stack trace you can see that the offending code is on line 194 in typos.js (which is line 196 in the file you have linked to). Array.reduce fails with a TypeError if the array is empty and there is no initial value specified. Providing an initiual value should help:

return typos.reduce(function(a, b) {
    return a.concat(b);
}, '');

Replace '' with the correct initial value, if needed.