javascript_flashcards

Question 1

Term

Answer 1

Definition

Question 2

const (JS)

Answer 2

For variables you can’t reassign after setting them, use this for most things.

Question 3

let (JS)

Answer 3

For variables you can reassign when needed.

Question 4

var (JS)

Answer 4

The old way with weird scoping, avoid using it.

Question 5

Strings (JS)

Answer 5

Text in quotes.

Question 6

Numbers (JS)

Answer 6

Can be whole numbers or decimals.

Question 7

Booleans (JS)

Answer 7

True or false values.

Question 8

Arrays (JS)

Answer 8

Ordered collections in square brackets that hold multiple items.

Question 9

Objects (JS)

Answer 9

Key-value pairs in curly braces where you access values by their property name.

Question 10

Function Declaration (JS)

Answer 10

Uses the function keyword followed by the function name.

Question 11

Arrow Function (JS)

Answer 11

Uses arrow notation which is the shorter modern syntax. Modern Lambda functions use arrow functions.

Question 12

async/await (JS)

Answer 12

Used for operations that take time like API calls or database queries. Makes asynchronous code read like synchronous code so it’s easier to understand. Use await to pause execution until a promise resolves. Handler function must be declared as async to use await inside it.

Question 13

Error Handling (JS)

Answer 13

Wrap risky code in try/catch blocks to handle errors gracefully. Catch errors from await operations so they don’t crash your function. Log errors and return default values so the call flow can continue.

Question 14

forEach (JS)

Answer 14

Loop through arrays to execute code for each item.

Question 15

map (JS)

Answer 15

Transform each item into something new.

Question 16

filter (JS)

Answer 16

Keep only items that match a condition.

Question 17

find (JS)

Answer 17

Get the first item that matches.

Question 18

Object Property Access (JS)

Answer 18

Access properties using dot notation or square brackets.

Question 19

Destructuring (JS)

Answer 19

Extract multiple values into individual variables in one line.

Question 20

Object Add/Update (JS)

Answer 20

Add or update properties by assigning a value to a property name.

Question 21

AWS SDK (JS)

Answer 21

Initialize services using new AWS followed by the service name. Call methods and add dot promise at the end to get a promise. Use await to pause until the promise resolves and get the result.

Question 22

Lambda Structure (JS)

Answer 22

Entry point is exports dot handler equals async function with event and context parameters. Extract input data from the event object that Amazon Connect passes in. Wrap logic in try/catch blocks for error handling. Return an object so Amazon Connect can use the values as contact attributes.

Question 23

Prototype (JS)

Answer 23

JavaScript’s inheritance system where objects inherit properties and methods from parent objects.

Question 24

Hoisting (JS)

Answer 24

JavaScript automatically moves variable and function declarations to the top of their scope.

Question 25

Scope (JS)

Answer 25

Where variables are accessible in your code. Can be global everywhere, function level inside functions, or block level inside curly braces.

Question 26

Closure (JS)

Answer 26

Function that remembers variables from its outer scope even after the outer function finishes.

Question 27

Callback (JS)

Answer 27

Function passed as an argument to another function that gets called later.

Question 28

Promise (JS)

Answer 28

Object representing eventual completion of async operation. Has three states: pending, fulfilled, or rejected.

Question 29

Spread Operator (JS)

Answer 29

Expands an array or object using three dots. Combines arrays or objects together.

Question 30

Template Literal (JS)

Answer 30

String that lets you embed expressions inside it using backticks. Easier than concatenating strings together.

Question 31

Truthy and Falsy (JS)

Answer 31

Values that evaluate to true or false in conditions. Falsy values are zero, empty string, null, and undefined. Everything else is truthy.

Question 32

null (JS)

Answer 32

Intentionally empty value you explicitly set to indicate nothing.

Question 33

this Keyword (JS)

Answer 33

Refers to the object that's currently executing the function.

Question 34

undefined (JS)

Answer 34

Variable has been declared but hasn't been assigned a value yet.

Question 35

Double Equals vs Triple Equals (JS)

Answer 35

Double equals converts types before comparing. Triple equals checks both type and value. Always use triple equals to avoid bugs.

Question 36

Map (JS)

Answer 36

Key-value pairs where keys can be any type, not just strings like regular objects.

Question 37

Array Methods (JS)

Answer 37

Built-in functions for working with arrays. map transforms each item, filter keeps items that match a condition, reduce combines all items into one value, find gets the first matching item, forEach loops through all items.

Question 38

JSON.parse (JS)

Answer 38

Converts a JSON string into a JavaScript object.

Question 39

JSON.stringify (JS)

Answer 39

Converts a JavaScript object into a JSON string.