Please answer to the question What are the basics concepts of Object-Oriented Programming

What selectors can set green background for second inner div in next markup?

<div class = "outer">

CSS selector which selects every <p> element that has no children

How to select multiple elements?

How do you display a border like this:

There is an HTML code to create To Do list:

Assume we have created listItem variable that holds element li to which we need to insert checkbox with label of an To Do item.

Please choose correct fragment of code to do this task.

Suppose we have

the function that calculates n! (n! = n*(n-1)*…*2*1). This function is

given below. Please restore the code covered up white rectangles.

Suppose we

need to check the correctness of login. It should consist of 8 characters:

lowercase and uppercase latin letters and digits. The login can’t start with

digit. Please select all valid regular expressions.

Specifies a

Square class with a side field and a method for calculating the perimeter of a square

class Square {
    constructor(side) {
        this.side = side;
    }
    calculatePerimeter(){
        return this.side * 4;
    }
}

What code implements asynchronous AJAX data transfer (for example from HTML form) by defining request headers and sending data to the server.