空格在Javascript中写为b

我正在尝试使用JavaScript完成python挑战,我被困在我的代码上

var letters = ["a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z"];

var userInput = "g fmnc wms bgblr rpylqjyrc gr zw fylb. rfyrq ufyr amknsrcpq ypc dmp.        bmgle gr gl zw fylb gq glcddgagclr ylb rfyr'q ufw rfgq rcvr gq qm jmle. sqgle qrpgle.kyicrpylq() gq pcamkkclbcb. lmu ynnjw ml rfc spj.";

for(x=0; x

代码的结果是:


  
ibhopebyoubdidntbtrundefinednslundefinedtebitbundefinedybhundefinedndbbthundefinedtsbwhundefinedtbcomputersbundefinedrebforbbdoingbitbinbundefinedybhundefinedndbisbinefficientbundefinedndbthundefinedtbsbwhybthisbtextbisbsoblongbbusingbstringbmundefinedketrundefinednsbbbisbrecommendedbbnowbundefinedpplybonbtheburlb


我的代码出了什么问题？