Javascript Regular Expressions - Required field validation

if (myField.value.match(/S/)) {
    // field is not empty
 }

/^s*$/.test(string)

var empty_string = /^s*$/; //create RegExp object for re-use

if (empty_string.test(myFormField.value))
{
  alert("Please be a bit more elaborate!");
}

/s/ or /S/

/^s+$/ or /^S+$/

if(string.match(/^s+$/)) {
   alert("string is empty!");
}

if(!string.match(/^S+$/)) {
   alert("string is empty!");
}