Quiz for Fundamentals of TypeScript, JavaScript and Node.js Quiz

splice is a very special method because we can also use it to
delete values. We specify the index from where we want to start deleting, and then the number of elements we want to delete.

In this question the concept of callback is used. In JavaScript callback is a function which is to be executed after another function has finished execution. A more formal definition would be – Any function that is passed as an argument to another function so that it can be executed in that other function is called as a callback function.
In the above mentioned code the function doSomething is called which in return will call the sayHi() function. Now the value of x is incremented after the sayHi() is called so console.log in side the sayHi() will print 1 and after that the value of x will be increased to 3. But it will be never used as the code ends.

JavaScript allows different numbers to be written in different formats/ kinds of numbers it can represent. Numbers can be written in
 decimals, exponentials, octal, hexadecimal, and binary formats. Consider the following code let binNr = 0b101;  it is in binary and its decimal equivalent is 5

The statement someConstant = 4; will generate error TypeError: Assignment to constant variable. const is used for variables that only get a value assigned once

Node. js is an open source JavaScript runtime environment that lets developers run JavaScript code on the server side. Node.js provide Javascript run-time environment that is built on Chrome’s JavaScript Engine(V8).

The length of the array is only counting the integer numbers starting from 0 up to the highest filed index. If there are elements in the middle of the sequence that do not have a value, they will still get counted. In this case, the length becomes 6.

This code will give an error ReferenceError that x is not initialized. This is because variables declared with let cannot be accessed before being defied, even within the same  block. 

In JavaScript, Console.log is a predefined function that accepts the value as an argument. At the time of code execution, console.log prints this value in the argument to the console. This code will print 1  4 and 7 in the console

The “any” type can be assigned any value without a type check, while the “unknown” type is a type-safe counterpart of “any” and can only be assigned a value after a runtime check or a type assertion.

The asynchronous message will be displayed after the synchronous message. This is because any function given to the setTimeout() function will be executed asynchronously, when the main thread is not busy anymore. So it will print 2 then 3 and then 1

The asynchronous message will be displayed after the synchronous message. This is because any function given to the setInterval function will be executed asynchronously, when the main thread is not busy anymore.
setInterval has the same behavior as setTimeout but the code is executed multiple times. You have to call clearInterval to kill the timer. 

There is no output statement like console.log() is used inside the function nor a value is returned . So as the function does not retuned any value so the last console.log statement will print undefined and no error will be generated.

The setTimeout() method calls a function after a number of milliseconds. 1 second = 1000 milliseconds. The setTimeout() is executed only once. Use the clearTimeout() method to prevent the function from starting.

The switch statement is normally used when evaluating more than four or five values. If we do not use break at the end of a case, it will execute the next case as well. This will be done from the case where it has a match, until the end of the switch statement or until we encounter a break statement. 

The asynchronous message will be displayed after the synchronous message. This is because any function given to the setTimeout function will be executed asynchronously, when the main thread is not busy anymore. So first Test 1 will be printed then Hello .
The time to wait before executing in milli seconds is optional . Default value is 0. So if no time to wait is specified it is considered as 0

Promises are used to handle asynchronous operations in JavaScript. In computer programming, asynchronous operation means that a process operates independently of other processes. Promises are the ideal choice for handling asynchronous operations in the simplest manner. 
Promise constructor takes only one argument which is a callback function. The callback function takes two arguments, resolve and reject . 
We  perform operations inside the callback function and if everything went well then call resolve. If desired operations do not go well then call reject.
In the quiz code we used a Promise function and make decisions on the basis of value of x and y. If the value of x and y is checked using ===. The strict equality operator ( === ) checks whether its two operands are equal, returning a Boolean result. As the values are different so reject part of the Promise function will be executed . Hence Some error has occurred will be printed

In JavaScript arrays can also contain other arrays . This
is called a multidimensional array. we can create an array of already existing arrays. This is called a two-dimensional array . The fist value is
assigned the position of 0, the second 1, the third 2, and so on

Modulus (%) is the operation in which you determine how much is left after dividing a number by another number in its entirety. The amount of times the number can fi in the other number does not matter here. The outcome will be the remainder, or what is left over. 

In JavaScript, the typeof operator returns the data type of its operand in the form of a string. The operand can be any object, function, or variable.

The possible types that exists in javascript are:

• undefined
• Object
• boolean
• number
• string
• symbol
• function

In JavaScript, “?” is called the ternary operator which is used for choosing one choice from the given two choices. The conditional (ternary) operator is the only JavaScript operator that takes three operands: a condition followed by a question mark (?), then an expression to execute if the condition is truthy followed by a colon (:), and finally the expression to execute if the condition is false.  ternary operator is used instead of if else statement and makes the code shorter.

var has global scope and let has block scope. var’s global scope means that you can use the variables defied with var in the entire script. On the other hand, let’s block scope means you can only use variables defied with let in the specifi block of code in which they were defied. 

The code will return Steve as this is the value at index 1 or current element .

The code will not generate any error and undefined will be printed in the log. It is due to the fact that we have used var to declare a variable . This is due to a phenomenon called hoisting, which means using a var variable before it’s been declared results in the variable being undefined rather than giving a ReferenceError.

We can have the increment operator after the operand (x++), in which case we call this the postfix unary operator. The postfix gets executed after sending the variable through, and then after that, the operation gets executed. 

Arrays are lists of values. These values can be of all data types and one array can even contain different data types. It is often very useful to store multiple values inside one variable.

JavaScript can have mixed arrays and arrays can hold any type of
variable. The values of the array won’t be converted to a single data type or anything like that. JavaScript simply stores all the variables with their own data type and
value in the array

There is no meaning to assign void to a variable, as only null or undefined is assignable to void. So Error will be generated

We can import entire module or single package using following commands

1. Importing an entire module:
   import * as name from ‘module-name’
2. Import default export from a module:
   import name from ‘module-name’
3. Importing a single export from a module:
   import { name } from ‘module-name’
4. Importing multiple exports from a module:
   import { nameOne , nameTwo } from ‘module-name’

ff you wish to delete an item from array we can use the delete operator for this purpose.  This is not a method, but you can use it
to change the value of a certain position of the array to undefied. 

for loop in Javascript first initializes the variable and later on checks for the condition expression and after that execute the line of statements. The value of iterator i increase until it reaches the value of length. This for loop will execute 3 times and print value of a which is 5 three time.

Concurrency means multiple computations are happening at the same time. In other words Concurrency is whenever things are happening “at the same time” or in parallel. Concurrency is everywhere in modern programming, 

The indexOf() method of array returns the index on which the value is found. If a value occurs in an array more than once, it will return the fist occurrence. If the value is not found, it will return -1

JavaScript is a single-threaded synchronous programming language.
It means that the main thread where JavaScript code is run, runs in one line at a time manner and there is no possibility of running code in parallel.
The event loop is the secret by which JavaScript gives us an illusion of being multithreaded even though it is single-threaded.

In JavaScript ** is known as Exponent Operator. Exponentiation means raising a certain base number to the power of the exponent, for example, xy. This can be read as x to the power of y. It means that we will multiply x by itself y number of times. 

The Math.ceil() function always rounds up and returns the smaller integer greater than or equal to a given number. 

In TypeScript, “undefined” is used to indicate the absence of a value, while “null” is used to indicate a value that is intentionally empty.