javascript – Help to solve a problem with my JavaScrip code (can not read the property & # 39; style)

Greetings I create a payment registry section where the user then chooses the package that suits you. You can select the days and times that suit him. Start by hiding the days and hours options as they complete the form. but after the user has chosen a plan, it will be deployed with the help of style.display = "block"; the content but I get this error Could not read the style property & # 39; of null
at HTMLInputElement.showDays
. Here, I leave the code with which I work. Thank you in advance for any advice or help.

function showDias () {
var MondayPrinc = parseInt (uno_princ.value, 10) || 0
TuesdayPrinc = parseInt (uno_princ.value, 10) || 0
WednesdayPrinc = parseInt (uno_princ.value, 10) || 0
ThursdayPrinc = parseInt (uno_princ.value, 10) || 0;

var horaElegidas = [];

if (martesPrinc> 0) {
horaElegidas.push ("Monday," Tuesday, & # 39; Wednesday, & # 39; Thursday & # 39;);
}
for (var i = 0; i <horaElegidas.length; i ++) {
document.getElementById (TimeElegados[i]) .style.display = & # 39; block & # 39 ;;
}
}