在运行使用MyClass的代码后，您正在定义MyClass。此外，将您的类填充到变量而不是将其称为传统方式会导致一些问题。试试这个：

You are defining MyClass after you run the code that uses MyClass. Also, stuffing your class into a variable rather than declaring it the "traditional" way causes some problems. Try this:

function MyClass ($element) {

  this.$element;
  console.log(this.$element);

  // more code...
}

$('.js-container').each(function (i, element) {
  new MyClass($(element));
  console.log($(element));
});

此外，移动 MyClass.prototype。实际MyClass中的定义。把它们放在后面。

Also, move your MyClass.prototype. definitions out of the actual MyClass. Put them after.