allow only one space between to words

function checkSpace()
{
var flg=1;
var txt = document.getElementById('TextBox1').value;

var strArr = new Array();
strArr = txt.split(" ");
for(var i = 0; i < strArr.length ; i++)
{
if(strArr[i] == "")
{
alert("Only one space is allowed between words");
flg=0;
break;
}
}