在nodejs中有这样一段代码可以使得控制台输出显示颜色，process.stderr.write('\u001b[31m error \u001b[0m :)

下面是摘自维基百科的一段内容：

The original specification only had 8 colors, and just gave them names. The SGR parameters 30-37 selected the foreground color, while 40-47 selected the background. Quite a few terminals implemented "bold" (SGR code 1) as a brighter color rather than a different font, thus providing 8 additional foreground colors. Usually you could not get these as background colors, though sometimes inverse video (SGR code 7) would allow that. Examples: to get black letters on white background use ESC[30;47m, to get red use ESC[31m, to get bright red use ESC[31;1m. To reset colors to their defaults, use ESC[39;49m (not supported on some terminals), or reset all attributes with ESC[0m. SGR code

其中有几个关键词：ESC,SGR code, CSI codes

Unicode Character 'ESCAPE' (U+001B) 原来U+001B在unicode编码中就是被定义为转义字符 请戳这里：ESC 【备注：Unicode code points appear as U+】

most of the sequences are more than two characters and start with the characters ESC and [ (left bracket/0x5B). This sequence is called CSI for Control Sequence Introducer (or Control Sequence Initiator)

|Code| Name| Effect| |--|--| |CSI n m|Select Graphic Rendition|Sets SGR parameters, including text color. After CSI can be zero or more parameters separated with; . With no parameters, CSI m is treated as CSI 0 m (reset / normal), which is typical of most of the ANSI escape sequences.|

结论： process.stderr.write('\u001b[31m error \u001b[0m) 前面的\u001b[31m用于设定SGR颜色，后面的\u001b[0m相当于一个封闭标签作为前面SGR颜色的作用范围的结束点标记。 这等价于 process.stderr.write('\033[31m error \033[0m) （注意033前面的** \ **是必须加的,这在javascript中才会被识别为八进制的33,即c++中的\u001B）