Which of the following API is a MUST for every ReactJS component?

What does the following JavaScript code snippet do?
data.sort(function(a,b),b-a);

Babel is

Which one of the following is the correct output for the given JavaScript code?

const object1 ={};
a = Symbol('a');
b =Symbol.for('b');
object1[a]='harry';
object1[b]='derry';
constobjectSymbols=Object.getOwnPropertySymbols(object1);
console.log(constobjectSymbols.length);

Which one of the following is correct output for the following given JavaScript code:

var obj=
{
length:20,
height:35,
}
if('breadth' in obj === false)
{
obj.breadth = 12;
}
console.log(obj.breadth);

When interpreter encounters an empty statements, what it will do:

What is used in ReactJs to increase performance del

Choose the client-side JavaScript object:

What will be the function of the following JavaScript code?

var scope = "global scope";
function checkscope()
{
var scope = "local scope";
function f()
{
return scope;
}
return f;
}

Which one of the following operator is used to check weather a specific property exists or not:

Every object contains three object attributes that are _______.

Before updating the user interface, React uses which algorithm to compare the new tree with the most recent tree to find out the most efficient way to update the user interface

Scripting language are

In JavaScript, Window.prompt() method return true or false value ?

What is the declarative way to render a dynamic list of components based on values in an array