js4---函数开始前的语句学习
算数运算符:14~26
https://www.bilibili.com/video/BV1YW411T7GX?p=27&vd_source=33a473c8377a5f615680389ca854f967
句,相信大家都懂
那么块,就是用{ }套起来就可
28~45:
https://www.bilibili.com/video/BV1YW411T7GX?p=46&vd_source=33a473c8377a5f615680389ca854f967
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课程a:if语句

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课程b:

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课程c:while
