javascript - How to understand this onclick statement?

Question

is link[i].onclick = Why are the two brackets ()() used together? How to understand?

As shown below:

Please tell me! Thanks!

Answer 1

Assumption:

var test = function(i) {
    return function() {
        alert(i+1);
    }
}

So your above line can also be written like this:

links[i].onclick = test(i);

The first bracket is to wrap the function name, and the second bracket is to indicate the method parameters

Answer 2

Self-executing function, indicating that it directly points to the content of function return.