check first two number jquery
// Will work for " 123433 " or "12345634 ", etc. var value = $(this).val(), re = /^\s*(\d{4})(\d+)\s*$/, // better to initialize only once somewhere in parent scope matches = re.exec(value), expectedCode = 3541, expectedLength = 13; if(!!matches) { var code = matches[1]; // first group is exactly first 4 digits // in matches[2] you'll find the rest numbers. if(value.length == expectedLength && code == expectedCode) { // Change the color... } }
