For example, in the axios documentation
axios#get(url[, config])
axios#delete(url[, config])
axios#head(url[, config])
get(url[,config]) The config parameter indicates optional get(url,[config]) This config also indicates optional, both are What's the difference? How to write the comma inside
and the comma behind it:
jquery: hover([over,]out) and hover([over] ,out) What’s the difference?
This kind of comma is at the end, and the square brackets also indicate optional
Where is this syntax or writing specification defined? How can I find this way of writing? What about the description
![[Web front-end] Node.js quick start](https://img.php.cn/upload/course/000/000/067/662b5d34ba7c0227.png)
I haven’t read the documentation of axios.
My understanding is:
get(url[, config])This representation can write two parameters or one parameter, the latter one is optional;get(url[, config])这种表示可以写两个参数或一个参数，后一个是可选的；get(url,[config])这种表示必须写两个参数，后一个config虽然可选，但是没有的时候要传null；hover([over,]out)这种表示你写两个参数的时候分别作为over和out传进函数，而如果只有一个参数那就是out；hover([over],out)get(url,[ config])This representation must write two parameters. Although the latter config is optional, null must be passed if it is not available;hover([over,]out)This representation When you write two parameters, pass them into the function as over and out respectively, and if there is only one parameter, it is out;
🎜Nowadays, most plug-ins can recognize the number of parameters, so it seems that there are very few cases where commas are written outside and null placeholders need to be passed. 🎜hover([over],out)The meaning is the same as above: it must be passed when there is no over Enter null;