Set the default value of function parameters in js (suitable for the absence of parameter passing)

Today, I encountered a problem when I wrote a class library for div + css to simulate js information boxes. I want to automatically use "prompt information" as the window title when I didn't pass the parameter. I tried to write it like this.
Copy codeThe Code is as follows:
Function MessageBox (title = ""){
}

No doubt I failed to run (or I will not post this blog post)

Finally, Baidu found such a good thing.
Copy codeThe Code is as follows:
Function test (){
Var B = arguments [0]? Arguments [0]: 50;
Return a + ':' + B;
}

According to my understanding, arguments is probably something similar to an array. The subscript starts from 0 and represents the parameters of this function in sequence.

For example, in the previous example, arguments [0] indicates parameter.

Actually arguments [0]? Arguments [0]: 50 can also be written as: arguments [0] | 50; the writing method is quite simplified. The above is the method for setting the default value of the function parameter in js.