Chapter 8 : Introduction to JavaScript Flashcards by Wl hoe

Who invented JavaScript?

Brendan Eich ( 1995 )

Java
- General Purpose Programming Language
  JavaScript
- Used on websites to make them animated and interactive

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List out 5 examples that JavaScript can do?

Change HTML content
Change HTML attributes
Change HTML styles ( CSS )
Hide HTML elements
Show HTML elements

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What HTML tag is used for JavaScript , CSS?

```
<script>

</script>
```
<style>
</style>

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When does the JavaScript function called?

Executed when the JavaScript function called

A function can be called when an event occurs, like when the user clicks a button

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What is the file extension for JavaScript files?

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How to link external JavaScript ?

Can be placed inside < head > or < body >

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What is the advantages of JavaScript? ( 3 )

Separates HTML and code
Makes HTML and JavaScript easier to read and maintain
Cached JavaScript files can speed up page loads

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How to add several script files?

<scri[t src=”myScript1.js”>
</script>

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List out 4 ways that JavaScript can display data

window.alert() - Alert Box
document.write() - Write into HTML Output
innerHTML - Write into HTML element
console.log() - Write into Browser Console

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How to show window alert of 5 + 6 ?

<!DOCTYPE html>

<script>
window.alert(5+6);
</script>

</body>
</html>

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How to use document.write() to show 5 + 6 ?

<!DOCTYPE html>

Write the answer 11 where the code is placed

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How to display new paragraph for 5 + 6 using JavaScript?

<!DOCTYPE html>

<script>
**document.getElementById("demo").innerHTML = "<h2>5 + 6</h2>";**
</script>

</body>
</html>

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How to write the total amount for 5 + 6 into browser console?

<!DOCTYPE html>

<script>
console.log(5+6)
          <script>
     </body>
</html>
</script>

</body></html>

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What is JavaScript Syntax?

JavaScript syntax is the set of rules of how JavaScript programs are constructed

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List out 5 statements that JavaScript are composed of

Values
Operators
Expressions
Keywords
Comments

Statements are being executed one by one, in the same order as they are written

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What are program instructions called?

Statements

What is JavaScript statement seperated by?

Semicolons

List out JavaScript Arithmetic Operators ( 7 )

List out JavaScript assignment operator ( 6 )

=
+=
-=
*= ( x = x * y )
/=
%=

List out JavaScript Comparison Operators ( 9 )

==
=== ( Equal value and equal type )
!=
!== ( Not equal value and not equal type )
>
<
> =
<=
?

List out 2 JavaScript Type Operators

typeof
- Returns the type of a variable
instanceof
- Returns true if an object is an instance of an object type

What are JavaScript comments being used to? ( 2 )

Explain JavaScript code, and to make it more readable
Prevent execution, when testing alternative code

List out :
1. Single Line Comments
2. Multiline Comments

//
Starts with /* , End with */

What are variables used for?

Containers for storing data values

What does all JavaScript variables must be identified with?

1. Unique names - It is called Identifiers * Can be short names ( x , y ) or more descriptive names ( age, sum, totalVolume )

List out general rules for construction names for variables ( 6 )

1. Names can contain letters, digits, underscores, and dollar sign 2. Names must begin with a letter 3. Names can also begin with $ and _ 4. Names are case sensitive 5. Reserved words ( JS Keywords ) cannot be used as names 6. JavaScript identifiers are case-sensitive

What keyword can we use to declare JavaScript variable? ( 3 )

1. var 2. let 3. const * let and const are added in 2015

How to create a variable using the var keyword?

1. var carName * The variable has no value ( Technically it has the value of undefined ) carName = "Volvo" to assign data with the assignment operator var carName = "Volvo" assign a variable when we declare it

List out 4 dataTypes that the var keyword can handle

1. String 2. Numbers 3. Array 4. Object * And more

How to assign string John Doe to var userName?

1. var userName = "John Doe"; * Can use "" or '' ( Double / Single Quotes ) * var ans = "He is called 'Johnny'" / 'He is called "Johnny"' * We cannot type "He is called "Johnny""

How to assign value 30 to variable age?

1. var age = 30; * Decimals var price = 29.99 * Exponential var y = 123e5 ( 12300000 ) var z = 123e-5 ( 0.00123 )

What is the dataType for user input?

1. String

What method is available to convert user input string value into number? ( 3 )

1. Number() - Converts an object's value to a number 2. parseFloat() - Parses a string and returns a floating point number 3. parseInt() - Parses a string and returns an integer Number("10"); parseInt("-10"); parseInt("10 20"); parseInt("10 Years");

What symbols are used to write Arrays?

1. Square Brackets []

How to declare a variable cars to store 3 values Saab, Volvo and BMW?

1. var cars = ["SAAB" , "Volvo" , "BMW"] * Array items are seperated by commas

What symbols are used to write JavaScript objects?

1. Curly braces {}

How to create an objects that stores user first / last name, age and eye color?

1. var person = { firstName : "John" , lastName : "Doe" , age : 50, eyeColor : "Blue"}