js sets the default value of function parameters (suitable for cases where no parameters are passed)_javascript skills

Today I encountered a problem when writing a div css class library that simulates a js information box. I hope that when I don't pass parameters, "prompt information" will be automatically used as the window title. I tried to write like this

Copy code The code is as follows:

function MessageBox(title="" ){
}

There is no doubt that my operation failed (otherwise I wouldn’t have posted this blog post)

Finally after some Baidu, I found this Good stuff

Copy code The code is as follows:

function test(a){
var b=arguments[0]?arguments[0]:50;
return a ':' b;
}

According to my humble understanding, arguments are probably similar to An array, with subscripts starting from 0, represents the parameters of the function in order

. For example, arguments[0] in the above example represents parameter a

. In fact, arguments[0] ?arguments[0]:50 can also be written as: arguments[0] || 50; The writing method is quite concise. The above is the method to set the default value of function parameter in js.