Support for missing parameters

[delvedor]

Using example.js as schema, this is the generated code:

function $main(obj) {
      var json = '{'

      if (obj.firstName !== undefined) {
        json += '"firstName":'
        json += $asString(obj.firstName)
        json += ','
      }

      if (obj.lastName !== undefined) {
        json += '"lastName":'
        json += $asString(obj.lastName)
        json += ','
      }

      if (obj.age !== undefined) {
        json += '"age":'
        json += $asNumber(obj.age)
        json += ','
      }

      if (obj.now !== undefined) {
        json += '"now":'
        json += $asString(obj.now)
        json += ','
      } else {
        throw new Error('now is required!')
      }

      if (obj.reg !== undefined) {
        json += '"reg":'
        json += $asString(obj.reg)
      }

      json += '}'
      return json
    }

If a parameter is required, there will be the else branch.

As you can see I'm not using obj.hasOwnProperty(prop) for testing the existence of the key (is commented inside the code), because I've noticed a big difference of performances.
When using obj.key !== undefined I get around 5 million ops/sec, instead if I use obj.hasOwnProperty(prop) I get ~2 million ops/sec.

The problem is that obj.key !== undefined is not strict as obj.hasOwnProperty(prop).
Opinions?

[mcollina]

please close the '`' in the new line

[mcollina]

I agree on using !== undefined, if you are using a schema, you want that type. On the other end, I see why people would want that behavior. Put a comment to this PR in that place, something like "using !== for perf reasons, see #3 for discussion".

I'm 100% open to have a configuration switch to use hasOwnProperty but I don't think it's important at this stage of the project. So, if someone wants to implement it and send a PR, I'm happy to review it and merge.

Anyway, this is a major difference from JSON.stringify, so we should write it in the README.md.

[delvedor]

Totally agree with you, in the next commit I'll add the README and code changes.