\n 与 \r 的区别

近期的需求用到命令行输出的解析，在解析类似进度条的内容时，遇到一些问题。经过反复的搜索询问，大概得到答案：主要在于 \r 和 \n 的区别。StackOverflow 的一个答案是这么解释的：

As indicated by Peter, CR = Carriage Return and LF = Line Feed, two expressions have their roots in the old typewriters / TTY. LF moved the paper up (but kept the horizontal position identical) and CR brought back the “carriage” so that the next character typed would be at the leftmost position on the paper (but on the same line). CR+LF was doing both, i.e. preparing to type a new line. As time went by the physical semantics of the codes were not applicable, and as memory and floppy disk space were at a premium, some OS designers decided to only use one of the characters, they just didn’t communicate very well with one another ;-)

所以 \r 换行之后，光标移到此行的 0 位，继续输出，于是新的一行会替代旧的一行，形成的效果就是进度条在更新；而 \n 则会另起一行，形成多行输出的效果。

所以类似我这个需求，直接 line.split('\r').pop() 即可。

另外，new TextDecoder('utf-8').decode(binaryData) 返回的文本都是用 \r\n 做换行的。