Determining the operator from a string using javascript -

i need help.

i need come javascript function check string entered textbox determine sql operator

example:

var field1 = document.getelementbyid('field1').value  var field2 = document.getelementbyid('field2').value  var field3 = document.getelementbyid('field3').value  function validate(textbox) {  var operator  if ('%' first character placed before , after value) { operator = }  else if ('%' first character placed before value) { operator = }  else if ('%' last character placed after value) { operator = }  else { operator equals "=" } //default  alert(operator)   } 

example of function in action:

validate(field1) 

you can use regular expressions this. looks if string contains %, operator like. can this:

var operator = "=";  //if string starts % or ends % //the operator "like" if(/^%/.test(str) || /%$/.test(str)) {    operator = "like"; }