Discussion on the problem of parentheses in JS method calling_Basic knowledge

For the mobile html page,

wrote a function.

Copy the code The code is as follows:

function showAlert(msg,fn){
showDialog("alert", msg,"warm reminder",260);
if(isNull(fn) == false){
$( "#SD_confirm").unbind("click");
$("#SD_confirm").bind("click",fn);
}
}

function exist( ){

alert("aaa");

}

fn is a function, when calling it I wrote

Copy code The code is as follows:

showAlert(json.msg,exist());

As a result, when I reached this line of code, before I reached the showDialog method, I went to exist and aaa popped up. What happened? I later found out that I had written it wrong.

should be written as

Copy code The code is as follows:

showAlert(json.msg,exist);

In this way, the dialog prompt will pop up first, and then click OK to pop up aaa.

Damn it. It turns out that there was a mistake in the brackets. Sigh!