基于Redis 的任务队列Bull -- （七）process job

bull 通过 process 方法定义 job 的处理器，并且开始执行 job

name / concurrency 是可选参数，handler 是必选参数

默认的 name 是 Job.DEFAULT_JOB_NAME，concurrency 是 1

虽然 process 方法返回 Promise<any[]>，但是一般不会等待它

Queue.prototype.process = function(name, concurrency, handler) {
  switch (arguments.length) {
    case 1:
      handler = name;
      concurrency = 1;
      name = Job.DEFAULT_JOB_NAME;
      break;
    case 2: // (string, function) or (string, string) or (number, function) or (number, string)
      handler = concurrency;
      if (typeof name === 'string') {
        concurrency = 1;
      } else {
        concurrency = name;
        name = Job.DEFAULT_JOB_NAME;