html - How to get length of getElementsByTagName with javascript -

working through example code sort list of within :

function sortlist() {   var list, i, switching, b, shouldswitch;   list = document.getelementbyid("timelineul");   switching = true;   /*make loop continue until   no switching has been done:*/   while (switching) {     //start saying: no switching done:     switching = false;     b = list.getelementsbytagname("figcaption");     //loop through list items:     console.log(b);     console.log(b.length);     (i = 0; < (b.length - 1); i++) {       //start saying there should no switching:       shouldswitch = false;       /*check if next item should       switch place current item:*/       console.log(b[i].innerhtml);       console.log(b[i+1].innerhtml);       if (b[i].innerhtml.tolowercase() > b[i + 1].innerhtml.tolowercase()) {         /*if next item alphabetically lower current item,         mark switch , break loop:*/         shouldswitch= true;         break;       }     }     if (shouldswitch) {       /*if switch has been marked, make switch       , mark switch done:*/       b[i].parentnode.insertbefore(b[i + 1], b[i]);       switching = true;     }   } } 

console.log(b); produces this:

but, console.log(b.length); results in 0

how can number of items in b can iterate through them sort figures figcaptions?

this situation happens when javascript starts executing before html loaded. if case, might have wrap call sortlist() function within domcontentloaded event :

document.addeventlistener("domcontentloaded", function(e) {     sortlist(); });