Question

foo(a, b, c) function parameters (a, b, c) default definition

Here’s my code:

function foo(a, b, c) {


    // a, b, c default @param ?


};

or foo(a, b, callback) {} default callback ? thanks.

Answer 1

It just give in fo function;

function foo(a, b, callback) {

    // @param defaults
    (a || (a = "default a"));
    (b || (b = "default b"));


    // if  callback not function is function() {} --> callback();
    (callback || (callback = function() { return ""}));


    console.log(a, b, callback());

};

foo(); // default a default b undefined
foo("a--", "b--", function() { return "callback"}); // a-- b-- callback

or

function foo(a, b, callback) {

    // @param defaults
    var a = a || "default a";
    var b = b || "default b";

    // if  callback not function is function() {} --> callback();
    var callback = callback || function() {};

    console.log(a, b, callback());
};