Read command parameter (argument or option) from generator

getopt.js

function* getopt(argv) {

  let cache = null

  // ignore execution program & script filename by call to .slice() function.
  for (let node of argv.slice(2)) {

    const match = /^--([a-z][0-9a-z-]*)(?:=(.*))?$/i.exec(node)

    // hanlde cache first...
    if (cache) {

      // yield previous option with TRUE (no value matched) or current argument.
      const value = match ? true : node

      yield {
        name: cache,
        isArgument: false,
        value: value
      }

      cache = null

      // discard argument if assigned to previous option...
      if (match == null) {
        continue
      }
    }

    // save & continue if this option doesn't matched a value.
    if (match && !match[2]) {
      cache = match[1]
      continue
    }

    const mismatch = (match == null)

    yield {
      name: mismatch ? undefined : match[1],
      isArgument: mismatch,
      value: mismatch ? node : match[2]
    }
  }

  // handle last option without value
  if (cache) {
    yield {
      name: cache,
      isArgument: false,
      value: true
    }
  } 
}