All Questions

I'm working on a project and they gave me a C# file with code similar to what I had to do. Investigating it I found this:

valorOpcion1 = "valor_que_viene_de_un_lado";
valorOpcion2 = "valor_que_viene_de_otro_lado";

var miLista = new List<string>
    {
        $"opcion1:{valorOpcion1}",
        $"opcion1:{valorOpcion2}"
    };

What it does is define and initialize a list of strings with two default values. My doubt comes with the $one with those chains, I don't know what it is.

What does putting the dollar sign ( $) in front of a string do? Is there a difference between, say, "hola"and $"hola"?

The following code fails:

let obj1,obj2;
obj2 = {
  atributo: 'texto'
};

console.log(obj1.atributo);

Showing in console the message:

Uncaught TypeError: Cannot read properties of undefined (reading 'attribute')

In Firefox (v96) the message is:

Uncaught TypeError: obj1 is undefined

What does it mean and how can I fix it?

The pseudo-class :nth-childis often used in tables or lists to differentiate even rows from odd ones:

li:nth-of-type(2n) {
  background-color: #ccc;
}

<ul>
  <li>elemento1</li>
  <li>elemento2</li>
  <li>elemento3</li>
  <li>elemento4</li>
</ul>

Or to select a specific child element:

li:nth-of-type(3) {
  background-color: #F00;
}

<ul>
  <li>elemento1</li>
  <li>elemento2</li>
  <li>elemento3</li>
  <li>elemento4</li>
</ul>

However, it has a more complex syntax, I have seen cases of this style:

p:nth-child(4n+2)

I don't quite understand what exactly it does and what practical uses it can have.

I need to check if a number is greater than 50,000,000, but I want to avoid the typical:

if (numero > 50000000) {
   //....
}

Is there a way to check it with "regex", or another way?

I want to perform the concatenation of two String:

String nombre = adornoF.getNombre();
String prefijo = ga.getsid();
String all = nombre + prefijo;

As long getNombre()as getsid()they return a String.

Is it ok or is there a better way?