How to get “the day before a date” in javascript?

Question

These two stack overflow questions ask a similar question, but their solution doesn\'t seem to work for me: Javascript Yesterday Javascript code for showing yesterday's

Answer 1

var allmonths = [
    '01', '02', '03', '04', '05', '06', '07', '08', '09', '10', '11', '12'
];
var alldates = [
    '01', '02', '03', '04', '05', '06', '07', '08', '09', '10',
    '11', '12', '13', '14', '15', '16', '17', '18', '19', '20',
    '21', '22', '23', '24', '25', '26', '27', '28', '29', '30', '31'
];

var today = "2014-12-25";   
var aDayBefore = new Date(today);
aDayBefore.setDate(aDayBefore.getDate() - 1);

document.write(aDayBefore.getFullYear() 
  + '-' + allmonths[aDayBefore.getMonth()] 
  + '-' + alldates[aDayBefore.getDate() - 1]);