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)

JavaScript from Scratch: Getting Your Feet Wet

by Michael Girouard on Jun 03, 2008

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JavaScript from Scratch: Getting Your Feet Wet — Presentation Transcript

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