Javascript

Question 1

What is JavaScript?

Answer 1

JavaScript allows us to create incredibly diverse applications that run in the browser, on the back-end as NodeJS, on the desktop, and on mobile devices. It’s a flexible language, allowing us to program in many different styles — functional and object-oriented, in particular — mixing and matching concepts to adapt to our needs. It’s powerful, scalable, and has a robust community of developers churning out new code and advancing the language. And, finally, it’s a great first or second language to learn.

Question 2

What are variables?

Answer 2

• Hold primitive or compound data

- Types: Let & Const

Question 3

What is Let?

Answer 3

• Declares variable that can be changed later

Question 4

What is Const?

Answer 4

• Variable that cannot be changed

Question 5

What are the 2 types of data? (2)

Answer 5

• Primitive

- Compound

Question 6

What are the 2 types of data? (2)

Answer 6

• Primitive

- Compound

Question 7

What is Compound data?

Answer 7

• array

- object

Question 8

Define DOM

Answer 8

• Document Object Model

Question 9

What is the DOM?

Answer 9

__

Question 10

How to write an IF statement in JS

Answer 10

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Question 11

How to insert JS?

Answer 11

• Insert tag just before </body> of HTML doc containing link to .js file.
• real-life apps bundle many .js files into one

Question 12

What is asynchronous JS?

Answer 12

• The process of making requests for additional data from a loaded page

Question 13

Define AJAX

Answer 13

• Asynchronous JavaScript and XML

Question 14

How to write an IF statement in JS

Answer 14

if (condition) {
    // Block of code
}

Question 15

What is ECMAScript?

Answer 15

• JavaScript specification revised every yr since ES2015-ES2020

Question 16

How can I manipulate the DOM with JS?

Answer 16

• Open Chrome DevTools with Ctrl+Shift+J & open the JS Console

Question 17

What is a strict equality operator? (ex)

Answer 17

• returns true if two values are equal without performing type conversions
• 42 === 42
  true
• strict inequality operator is !==

Question 18

How to write an ELSE statement in JS

Answer 18

const age = 14;

let isAdult;

if (age >= 18) {
    isAdult = true;
} else {
    isAdult = false;
}
// => false

isAdult;
// => false

Question 19

How to write an ELSE IF statement in JS

Answer 19

const age = 20;

let isAdult, canWork, canEnlist, canDrink;

if (age >= 21) {
    isAdult = true;
    canWork = true;
    canEnlist = true;
    canDrink = true;
} else if (age >= 18) {
    isAdult = true;
    canWork = true;
    canEnlist = true;
} else if (age >= 16) {
    canWork = true;
}
// => true

isAdult;
// => true

canWork;
// => true

canEnlist;
// => true

canDrink;
// => undefined

Question 20

How to write a SWITCH statement in JS

Answer 20

const hunger = ‘famished’;

let food;

switch (hunger) {
    case 'light':
        food = 'grapes';
        break;
    case 'moderate':
        food = 'sushi';
        break;
    case 'famished':
        food = 'lasagna';
        break;
}
// => "lasagna"

food;
// => "lasagna"

Question 21

Ternary operator example

Answer 21

const age = 60;

const isAdult = age >= 18 ? true : false;

isAdult;
// => true

Question 22

How to write a function in JS?

Answer 22

function functionName(argument1, argument2, argument3) {
  body code goes here
}

Question 23

Objects

Answer 23

https://learn.co/tracks/cpb-v5/javascript/data-structures/objects

Question 24

For Loop

Answer 24

for (let i = 0; i < array.length; i++) {
  // Loop body
}

Question 25

While

Answer 25

while (j < myArray.length) {
console.log(myArray[j++]);
}

Question 26

How to iterate over an array

Answer 26

Use a for…of statement anytime you want to iterate over an array.

Question 27

How to iterate over an object

Answer 27

for (const  in ) {
  // Code in the statement body
}

Question 28

Traverse nested objects

Answer 28

userInfo.friends[0].firstName;
// => "Joe"

Question 29

Filter

Answer 29

[1, 2, 3, 4, 5].filter(function (num) { return num > 3; });
// => [4, 5]

Question 30

.map( )

Answer 30

const equippedEngineers = newEngineers.map(function(eng) {
    return Object.assign({}, eng, { equipment: 'Laptop' });
});

equippedEngineers;
// => [
//      { userID: 15, title: "Developer Apprentice", accessLevel: "admin", equipment: "Laptop" },
//      { userID: 63, title: "Developer Apprentice", accessLevel: "admin", equipment: "Laptop" },
//      { userID: 97, title: "Developer Apprentice", accessLevel: "admin", equipment: "Laptop" },
//      { userID: 12, title: "Developer Apprentice", accessLevel: "admin", equipment: "Laptop" },
//      { userID: 44, title: "Developer Apprentice", accessLevel: "admin", equipment: "Laptop" }
//    ]