Javascript Final

Question 1

What does ECMA stand for?

Answer 1

European Computer Manufacturer’s Association

Question 2

What is ECMA?

Answer 2

ECMA is a trademarked scripting-language specification standardized by ECMA international

Question 3

What is ECMA used for?

Answer 3

For client-side scripting and for writing server applications and services using Node.js

Question 4

What is a Shim?

Answer 4

A software add-in that provides full support for a particular software standard

Question 5

What are some examples of ECMAScript?

Answer 5

The “use strict” directive, for example String.trim(), Array.isArray(), Array.indexOf(), JSON.parse(), JSON.stringify(), property getters and setters and new object property methods

Question 6

What is a part of ECMA6?

Answer 6

Support for constants, Block Scope, Arrow Functions, Template literals, Modules, Classes, Promises etc…

Question 7

What are sets (set collections)?

Answer 7

Ordered lists of values that contain no duplicates. Accessed using keys

Question 8

What are maps?

Answer 8

the map object holds key-value pairs. Any value (both objects and primitive
values) may be used as either a key or a
value

Question 9

What are classes?

Answer 9

provides syntactical sugar. They offer a cleaner and more elegant syntax.

Question 10

Getters and setters

Answer 10

Properties are nouns, methods are verbs

Question 11

Inheritance

Answer 11

Concepts at higher levels are more general, concepts at lower levels are more specific(inherit properties of concepts at higher levels)

Question 12

Arrow Functions

Answer 12

Shorter way of creating simple functions, called lambdas in other languages.

Question 13

Are arrow functions named?

Answer 13

Arrow functions are not named, they can be assigned to a variable but are always anonymous

Question 14

Arrow function syntax

Answer 14

has a set of parentheses that will hold all the parameters like a function expression, next is the arrow =>, then the curly braces {} that will have the body of the function inside. Parentheses are optional only when one parameter is being passed. if no parameters are being passed, parentheses are required

Question 15

Example for a function

Answer 15

function literal (declaration)
function add1(a, b) {
return a + b;
}

Question 16

Example for function expression

Answer 16

let add2 = function (a, b) {
return a + b;
};

Question 17

Example for arrow function

Answer 17

let add3 = (a, b) => {return a + b;}

Question 18

Invocation of functions

Answer 18

Invoking a function suspends the execution of the current function, passing control and parameters to the new function. When the function is finished, it returns to the line following where it was invoked. It remembers where to return to because this information is stored on the stack prior to the function being invoked

Question 19

Return

Answer 19

the return statement can be used to cause the function to return early. A function always returns a value. If the value is not specified then undefined is returned

Question 20

Scope

Answer 20

controls the visibility and lifetimes of variables and parameters

Question 21

Scope variables

Answer 21

Variables and objects that are currently referenced are known as “alive”, deleted or moved out of scope or method finishes are de-referenced (no longer alive)

Question 22

Closure

Answer 22

the local variables for a function - kept alive after the function has returned

Question 23

Closure(cont)

Answer 23

Whenever you use a function inside another function, a closure is created. A closure in js is like keeping a copy of all the local variables, just as they were when a function exited

Question 24

What is Node.js

Answer 24

A platform for executing JavaScript base on non-blocking I/O. Uses an event driven model that enables fast scalable network applications

Question 25

Node.js(cont)

Answer 25

its a sever-side javascript for network applications. Supports modular JavaScript, utilizes non-blocking(asynchronous) code

Question 26

Node.js important info

Answer 26

Node.js is asynchronous by nature