JavaScript Basic Concepts B - About Methods

• methods are objects

This matter needs to be repeatedly emphasized. A method is an object of type Function, and like any other object, it has methods.

function gen() {
    return function ans(factor) {
        return 2 * factor;
    };
}

If it looks confusing, you can use variables to see

function gen() {
    var f = function ans(factor) {
        return 2 * factor;
    };
    return f;
}

or like this

function gen() {
    function ans(factor) {
        return 2 * factor;
    };
    return ans;
}

• How the method is named

Imagine you define the following method

function f(factor) {
    return 2 * factor;
}

same as below

var f = function (factor) {
    return 2 * factor;
};

f(2);

• way does not support polymorphism

You can't define two methods with the same name and hope to use different parameters to distinguish them. A method defined later overrides an earlier method.

function ans(f1, f2) { ... }

function ans(f1) { ... } // This replaces the previous method.

It should be noted that all parameters are not required

function ans(a, b) {
    //...
}
ans(2); // ans is called with a = 2, and b = undefined

• function return

In the method definition you can return any value or nothing

function () {
    if (cond1) {
        // return an object t
        return {
            a: 10
        };
    } else if (cond2) {
        // return undefined
        return;
    } else if (cond3) {
        // return a number.
        return 1;
    }
}