[12.1.函数的概念与作用](12.1.%E5%87%BD%E6%95%B0%E7%9A%84%E6%A6%82%E5%BF%B5%E4%B8%8E%E4%BD%9C%E7%94%A8.md) [12.2.函数的定义与调用](12.2.%E5%87%BD%E6%95%B0%E7%9A%84%E5%AE%9A%E4%B9%89%E4%B8%8E%E8%B0%83%E7%94%A8.md) [12.3.函数执行原理（重点/难点）](12.3.%E5%87%BD%E6%95%B0%E6%89%A7%E8%A1%8C%E5%8E%9F%E7%90%86%EF%BC%88%E9%87%8D%E7%82%B9-%E9%9A%BE%E7%82%B9%EF%BC%89.md) [12.4.函数参数（重点）](12.4.%E5%87%BD%E6%95%B0%E5%8F%82%E6%95%B0%EF%BC%88%E9%87%8D%E7%82%B9%EF%BC%89.md) [12.5.函数返回值（重点）](12.5.%E5%87%BD%E6%95%B0%E8%BF%94%E5%9B%9E%E5%80%BC%EF%BC%88%E9%87%8D%E7%82%B9%EF%BC%89.md) [12.6.可变函数](12.6.%E5%8F%AF%E5%8F%98%E5%87%BD%E6%95%B0.md) [12.7.匿名函数](12.7.%E5%8C%BF%E5%90%8D%E5%87%BD%E6%95%B0.md) [12.8.常用系统函数介绍](12.8.%E5%B8%B8%E7%94%A8%E7%B3%BB%E7%BB%9F%E5%87%BD%E6%95%B0%E4%BB%8B%E7%BB%8D.md)