Tux9000's questions

Seeking to understand about "literal templates" I was curious about the name and came across concepts like:

• " literal expressions "
• " string literals "
• " literal statements "

I also found that in the fields of mathematics and algebra there are concepts with the same name.

The point is that after consulting various definitions and looking for examples I could not clearly understand what a literal is , on the contrary I had more confusion, so I would like to allay my doubts about

• What exactly is a literal?
• How do you define and use a literal?
• what is a function literal?

Why is it that after defining a function through the browser console , " undefined " is returned ? Why happens? What would be missing in a function declaration for this not to happen?

For example, when creating a function with the following syntax, " undefined " is returned:

function miFuncion(algo){
    return algo;
}
//salida: undefined

Also if I use a syntax like the following, " undefined " is returned:

var miFuncion = function(algo){
    return algo;
}
//Salida: undefined

but, when you try something like:

miFuncion = function(algo){
    return algo;
}

change the return after the function is created, does anything change using this syntax?

I add a screenshot to make the idea that the question raises more objective

I have a doubt about the existence of the famous NaN , I would like to know, what is it for? What is your "existential meaning"?

So far the only thing I have been able to understand based on things I have seen in books and videos is that in summary it would be a kind of Error indicator in mathematical operations that usually warns us that there is an "invalidity" (such as multiplying a string for an integer); In addition, its data type is numeric and its value is undefined and different from any other value.

I am right? is it used for something else?

I add a couple of quotes:

NaN means "Not a Number". When a function or mathematical operation in JavaScript cannot return a specific number, it returns the value NaN instead. It is a property of the global object, and a reference to Number.NaN

JavaScriptNotes for Professionals - GoalKicker.com - Pg. 13.

It is a special static numeric property, NaN, which is equivalent to the global NaN, and is equivalent to Not-a-Number. Anytime you try to use a value in a numeric operation that can't be parsed as a number, you'll get a NaN error.

Javascript Cookbook, Shelley Powers - Pg. 56

NaN is short for Not-a-Number and represents an illegal number. It uses the isNaN() function to determine if a number is legal or valid according to the ECMA-262 specification.

JavaScript Step by Step 2ed. Steve Suehring - Pg. 63

The context of the question would be only in terms of its application in JavaScript, since talking about programming in general, arithmetic, computing or other topics would make the question much broader and it would become a bit ambiguous; on the other hand, I understand that the existence of an "Error", "message" or "alert" may be logical for a situation such as the one that can arise when operating irrational numbers or taking mathematical operations out of the mathematical "context", but , how can NaN differ from "typical" Error messages?

Can someone help me understand what is happening in this code?

public class unaClase extends Applet{
    public void paint(Graphics g){
        g.drawRect(0, 0, 400, 200);
    }
}

In my understanding it is something like that I create a class named aClass that inherits (because it becomes a child ) methods and attributes of the Applet class ; then it overrides the paint method (which was inherited from Applet ) and this method expects to receive an object (which we named g ) created from the Graphics class and then we call the drawRect method that is proper to the object g (which was created from the Graphics class ); so that when the class aClass is executed a rectangle is drawn , is it so?

Could I do something like this with C/C++?

    var a = 8;
        
    switch(a){ 
     case a>=12:
      console.log("a");
     break;
        
     case a>1 || a<6:
      console.log("aa");
     break;
        
     default:
      console.log("aaa");
     break;
    }

I tried something similar in C/C++ but I get an error when compiling, something like:

the value of 'a' cannot be used in a constant expression note: 'int a' is not a const

The code I tried was something like:

int miVar;
char letra;

cout<<"Digite el valor:"<<endl;
cin>>miVar;


switch(miVar){

    case miVar<=30000:
    letra = 'A';
    break;

    case (miVar>30000 & miVar<=60000):
    letra = 'B';
    break;

    default:
    letra = 'C';
    break;
}

I have been learning Javascript on my own, with the help of Videos, Books, Tutorials and more information that I have found on the internet; I have noticed that in several places they use + and , to concatenate elements, so I was wondering what is the correct way to concatenate in JS? What is the difference between using , (comma) and + (plus)? Is the same? On what occasions should I use one or the other?

I attach my example:

var numero = "numero";
var palabra = 55;

document.write(numero + palabra + "<br/>");
document.write(numero, palabra);

How could I make 1 function return 3 values ​​so that those 3 values ​​would serve as input parameters of another function (as if it were a callback --which in fact, I think it is--)?

So far I tried the following (although it did not work):

var resultado;
function num_2(repet){
	for (var i = 0; i > repet-1; i++) {
		if (i>=1) {
			return i + ", ";
		}else{
			return i;
		}
	}
}


function sumarr(a,b,c){
	if (a!="" && a!=null) {
		resultado = a+b+c;
		return "\n" + "resul: " + resultado + '\n' + "1: " +
		a + '\n' + "2: " + b + '\n' + "3: " + c + '\n' + '\n';
	}else{
		return "noting";
	}
}
console.log("\n" + "callback: " + sumarr(num_2(3)));