How javascript try…catch statement works

Question

I am trying to test in browsermob if certain input field work or not. I am attempting to use a try...catch statement which I have never used before. I know that the form is:

Answer 1

According to ECMAScript specifications,

try {
    // Code
} catch (varName) {  // optional if 'finally' block is present.
  if (condition) {   // eg. (varName instanceof URIError)
    // Condition (Type) specific error handling
  }
  else {
    // Generic error handling
  }
} finally {          // Optional if 'catch' block is present.
    // Execute this block after
    // try or after catch clause
    // (i.e. this is *always* called)
}