tsc运行后...

var week;

(function (week) {

    week[week["a"] = 1] = "a";

    week[week["b"] = 2] = "b";

    week[week["c"] = 3] = "c";

    week[week["d"] = 4] = "d";

    week[week["e"] = 5] = "e";

    console.log(week)

})(week || (week = {}));

直接打印结果出来：week（值）

{

  '1': 'a',

  '2': 'b',

  '3': 'c',

  '4': 'd',

  '5': 'e',

  a: 1,

  b: 2,

  c: 3,

  d: 4,

  e: 5

}

更直观一些