//?Define?the?callback?function. function?threeChars(value,?index,?str)?{????//?Create?a?string?that?contains?the?previous,?current, ????//?and?next?character. ????return?str.substring(index?-?1,?index?+?2); } //?Create?a?string. var?word?=?"Thursday"; //?Apply?the?map?method?to?the?string. //?Each?array?element?in?the?result?contains?a?string?that?has?the?previous,?current,?and?next?character. //?The?commented?out?statement?shows?an?alternative?syntax. var?result?=?[].map.call(word,?threeChars); //?var?result?=?Array.prototype.map.call(word,?threeChars);document.write(result); //?Output: //?Th,Thu,hur,urs,rsd,sda,day,ay