[严格模式](%E4%B8%A5%E6%A0%BC%E6%A8%A1%E5%BC%8F.md) [变量详解](%E5%8F%98%E9%87%8F%E8%AF%A6%E8%A7%A3.md) [数据类型](%E6%95%B0%E6%8D%AE%E7%B1%BB%E5%9E%8B.md) [typeof操作符](typeof%E6%93%8D%E4%BD%9C%E7%AC%A6.md) [undefined类型](undefined%E7%B1%BB%E5%9E%8B.md) [Null类型](Null%E7%B1%BB%E5%9E%8B.md) [Boolean类型](Boolean%E7%B1%BB%E5%9E%8B.md) [Number类型](Number%E7%B1%BB%E5%9E%8B.md)