Week 5 Flashcards by J L

When JavaScript manipulates a page or responds to user actions, what is it called?

Event Handling

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JavaScript can…

Dynamically update _______ (CKE)
Manipulate ____ and ___
Manipulate and validate ____

Content, HTML and CSS, Data

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As a developer

JavaScript cannot…

Write data permanently to an existing file
Access files on the server
Get data from the server database
Handle file uploads

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JavaScript was introduced by NetScape in ____
JavaScripts biggest update was in 2015 when ___ was released, the ___ version

1996, ES6, 6th

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Is JavaScript interpreted or compiled?

Interpreted

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JavaScript’s key construct is the ________

function

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3 ways to add JavaScript to an HTML page. Which way is recommended?

Embed, Inline, Link

Link is recommended

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T/F - To embed a script with JavaScript, just add the code as part of a script element

True

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To link a JavaScript file, just like a CSS file, where does the link go?

In the HTML pages head

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<!DOCTYPE html>

</head>
<body>
<button> Click Me! </button>
</body>
</html>

Will myFunction() link to the JavaScript function?

Yes

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How do comments in JavaScript compare to Java?

They are identical

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alert()

Display content with a pop up box

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prompt()

DIsplays a message and an input field within a modal window

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confirm()

Displays a question in a modal window with ok and cancel buttons

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console.log

Display content in the browsers JavaScript console

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document.write()

outputs the content (as markup or code) directly to the HTML document

What does markup mean?

Markup is the series of characters, symbols, and language that organizes and defines how the content looks, It is the code.

T/F - Each browsers console tab includes a text that you can use to enter your expressions or statements

True

T/F - You can execute multiple statements in the console by separating each statement with a semicolon

True

3 ways JavaScript code executes:

Auto, when the page loads
When your script calls a function
In response to some event, such as the user clicking a button

JavaScript variables are dynamically _____, declared with the ___ or ___ keyword and are ____ _________

typed, let or var keyword, case senstiive

What does typeof do in JavaScript?

Figures out a given variables type

What is the default value and type of a declared but uninitialized varaible?

Undefined and undefined.

Do we use camelCasing for JavaScript?

yes

T/F - In JavaScript, a variable can be declared after it has been used

True, it's called hoisting

Explain hoisting in JavaScript

It's JS's default behavior of moving declarataions to the top

Explain the difference between "var" and "let" during these 3 scenarios Scope Re-declaration Hoisting

Scope * var declarations are function-scoped. * let variables are block-scoped. Re-declaration * var variables can be updated and re-declared within the scope. * let variables can be updated but not re-declared. Hoisting * var variables are hoisted with an initial value undefined. * let variables are not hoisted with an initial value

In JavaScript the "numbers" datatype represents ________ and ________-_____ numbers

integers and floating point

An "object" in JavaScript includes ________ and ______

functions and arrays

T/F - In JavaScript, strings can only be double quotes

False, they can be both double and single quotes

What happens in each of these variable cases? 1. let a = "10"; let b = 20; console.log(a+b) 2. let a = "10"; let b = 20; console.log(+a+b) 3. let a = "10"; let b = 10; console.log(a-b) 4. let a = "10"; let b = true; console.log(a-b) 5. let a = "hello"; let b = "world"; console.log(a-b)

1. 1020 2. 30 - the 10 gets converted to a int the by unary operator (+) 3. 0 (converted to int by the -) 4. 9 (true = 1 when converted) 5. NaN

Name the string PROPERTY that can be used to see how long a string is stringName.

stringName.length

When using the Boolean() function, what are the values that will return false? what will return true?

False: 0, 0.0, NaN, empty string "", null, and undefined True: anything else

JavaScript operators: +, -, /, *,... 3 more

% modulo division ++ increment -- decrement

JavaScript Assignment Operators: a += b a *= b a %= b What do these do?

a = a+b a = a*b a = a%b

T/F - else-if behaves the same way as if-else in Java

True

All loops in JavaScript must consist of 3 things, what are they?

Incrementor Conditional expression Logic to increase the incrementor