<html>
<head>
<script>
function checkBlankSpace(str){
while((" ")>=0){
str = (" ","");
}
if( == 0){
alert("Input cannot be all empty");
}
}
function test(){
var testStr = ("test").value;
checkBlankSpace(testStr);
}
</script>
</head>
<body>
<input type="text" />
<input type="button" value="test" onclick="test()">
</body>
</html>