JavaScript from Scratch: Getting Your Feet Wet
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Transcript of JavaScript from Scratch: Getting Your Feet Wet
JavaScript From Scratch“Getting Your Feet Wet”
Agenda
• Variables
• Conditionals
• Loops
• Functions
Variables are...
• Storage Containers for Data
• Someone’s name
• A username/password
• The current time
• ... or anything else your application needs
var password = ‘mike is awesome’;
var name = ‘Mike G’;var age = 25;var isCool = true;
Conditionals are...
• A way to execute code conditionally
• If something is true, do this
• Otherwise, do that
var age = 25;
if (age < 21) { alert(‘Go home’);}
var age = 25;
if (age < 21) { alert(‘Go home’);}else { alert(‘Two drink minimum’);}
Loops
• Loops allow code to run repeatedly
• Over and over and over...
• But only upon a condition
var start = 10;var stop = 20;var counter = start;
while (counter <= stop) { alert(counter); counter = counter + 1;}
About those operators
=var foo = 100;
About those operators
==(foo == 100)
About those operators
<(age < 21)
About those operators
>(calories > 2000)
About those operators
<=(age <= 21)
About those operators
>=(calories >= 2000)
About those operators
&&(age >= 25 && age <= 50)
About those operators
||(name == ‘mike’ || name == ‘joe’)
Functions
• Store “blocks” of code so they can be reused later
• Are one of the most powerful features of the JavaScript language
function add () { alert(2 + 2);}
add();
function add (num1, num2) { alert(num1 + num2);}
add(2, 2);add(42, 10);add(123, 0);
function add (num1, num2) { return num1 + num2;}
var sum1 = add(2, 2);var sum2 = add(42, 10);var sum3 = add(123, 0);
Review
• Variables...
• Store data
• Begin with a var
• Are given names
• Are assigned values with =
Review
• Conditionals...
• Fork code execution based on a condition
• Begin with an if
• Condition enclosed in (parenthesis)
• Blocks are enclosed in {curly braces}
Review
• Conditionals...
• Can use else to catch a failed conditional
Review
• Loops...
• Repeatedly execute blocks of code
• Execute conditionally
• Come in many flavors:
• while, for, for in, do while
Review
• Functions...
• Store code for later use
• Can accept input parameters (arguments).
• Can send output (return values).
Homework
• Build a micro-library which performs basic math operations
• Functions should accept arguments and return the result of the math operation
Homework
• Required Functions:
• add (num1, num2)
• subtract (num1, num2)
• multiply (num1, num2)
• divide (num1, num2)
Homework
• Required Functions:
• square (num)
• increment (num)
• decrement (num)
• power (num, power)