Tried to append span into list appendchild(span) it is throwing an error?

var listcheck=document.getElementsByTagName("LI");
var span=document.createElement("SPAN");
for(var i=0;i<=listcheck.length;i++)
{
var span=document.createElement("SPAN");
var txt = document.createTextNode("\u00D7");
span.className = "close";
span.appendChild(txt);
span.textContent="X";
span.className+="closeicon";
listcheck[i].appendChild(span);
}

function searchinput()
{
	var li=document.createElement("li");
	var inputtext=document.getElementById("client_course").value;
    var t = document.createTextNode(inputtext);
document.getElementById("myUL").appendChild(li);
li.appendChild(t);
}