In this code, spot the comments, variables, operator, function, argument, and return value.
function calculateTip(total) {
var tipPercent = 0.15; //Can be changed
return (total * tipPercent);
}
var billPreTip = 10;
var billTip = calculateTip(billPreTip);
var receipt = 'Meal: ' + billPreTip + ' Tip: ' + billTip +
' Total: ' + (billPreTip + billTip);
console.log(receipt);
The scope of a variable is how long the computer will remember it.
A variable declared outside a function has a global scope and can be accessed anywhere, even in a function.
var awesomeGroup = 'Girl Develop It'; //Global scope
function whatIsAwesome() {
console.log (awesomeGroup + ' is pretty awesome.'); //Will work
}
whatIsAwesome();
A variable declared within a function has a local scope and can only be accessed within that function.
function whatIsAwesome() {
var awesomeGroup = 'Girl Develop It'; //Local scope
console.log ('I made a variable called awesomeGroup with a value of ' + awesomeGroup); //Will work
}
whatIsAwesome();
console.log (awesomeGroup + ' is pretty awesome.'); //Won't work
Boolean variables represent the logical values True and False
var catsAreBest = true;
var dogsRule = false;
If you try to use another variable as a boolean, JavaScript will guess. The number 0, the empty string ' ', undefined, and null are considered false, everything else reads as true.
Use if to decide which lines of code to execute, based on a condition.
if (condition) {
// statements to execute
}
var bananas = 5;
if (bananas > 0) {
console.log ('You have some bananas!');
}
Example | Name | Result |
---|---|---|
a == b | Equal | TRUE if a is equal to b (can be different types). |
a === b | Identical |
TRUE if a is equal to b, and the same type. |
a != b | Not equal | TRUE if a is not equal to b (can be different types). |
a !== b | Not identical |
TRUE if a is not equal to b, or they are not the same type. |
a < b | Less than | TRUE if a is strictly less than b. |
a > b | Greater than | TRUE if a is strictly greater than b. |
a <= b | Less than or equal to | TRUE if a is less than or equal to b. |
a >= b | Greater than or equal to | TRUE if a is greater than or equal to b. |
Don't mix up = and ==
Make a variable called "temperature." Write some code that tells you to put on a coat if it is below 50 degrees.
Use else to provide an alternate set of instructions.
var age = 28;
if (age >= 16) {
console.log ('Yay, you can drive!');
} else {
console.log ('Sorry, but you have ' + (16 - age) +
' years until you can drive.');
}
If you have multiple conditions, you can use else if.
var age = 20;
if (age >= 35) {
console.log('You can vote AND hold any place in government!');
} else if (age >= 25) {
console.log('You can vote AND run for the Senate!');
} else if (age >= 18) {
console.log('You can vote!');
} else {
console.log('You can\'t vote, but you can
still write your representatives.');
}
Modify your "wear a coat" code for these conditions:
Example | Name | Result |
---|---|---|
a && b | And | TRUE if both a and b are TRUE . |
a || b | Or | TRUE if either a or b is TRUE . |
! a | Not | TRUE if a is not TRUE . |
You can use these operators to combine conditions.
var bananas = 5;
if (bananas >=2 && bananas <7) {
console.log ('You have a reasonable number of bananas');
} else {
console.log ('Check your banana supply');
}
Add a logical operator to your what to wear program.
While will repeat the same code over and over until some condition is met.
var bottlesOfBeer = 99;
while (bottlesOfBeer >= 1) {
console.log (bottlesOfBeer + ' bottles of beer on the wall');
bottlesOfBeer = bottlesOfBeer - 9;
}
Make sure something changes in the loop, or your loop will go on forever...
For loops are very similar, but you declare a counter in the statement.
//will count 1 to 10
for (var i = 1; i <= 10; i++) {
console.log (i);
}
You can add other statements or logical operators inside the loops.
//Count from 1 to 50
for (var i = 1; i <= 50; i++) {
console.log (i);
//Says 'Buzz' after multiples of three
if (i % 3 == 0) {
console.log (' Buzz');
}
//Says 'Bang' after multiples of five
if (i % 5 == 0) {
console.log (' Bang');
}
}
To exit a loop, use the break statement.
//Count from 100 to 200
for (var i = 100; i <= 200; i++) {
console.log('Testing ' + i);
//Stop at the first multiple of 7
if (i % 7 == 0) {
console.log('Found it! ' + i);
break;
}
}
Write a loop that gives you the 9's times table,
from 9 x 1 = 9 to 9 x 12 = 108.
Finish early? Try using a loop inside a loop to write all the times tables, from 1 to 12.
Arrays are ordered lists of values.
var arrayName = [element0, element1, ...];
You can put different types of data into an array.
var rainbowColors = ['Red', 'Orange', 'Yellow', 'Green',
'Blue', 'Indigo', 'Violet'];
var lotteryNumbers = [33, 72, 64, 18, 17, 85];
var myFavoriteThings = ['Broccoli', 1024, 'Sherlock'];
The length property tells you how many things are in an array
var rainbowColors = ['Red', 'Orange', 'Yellow', 'Green',
'Blue', 'Indigo', 'Violet'];
console.log(rainbowColors.length);
You can access items with "bracket notation" by using the position of the object you want. Programmers start counting at zero.
var rainbowColors = ['Red', 'Orange', 'Yellow', 'Green',
'Blue', 'Indigo', 'Violet'];
var firstColor = rainbowColors[0];
var lastColor = rainbowColors[6];
You can use bracket notation to change an item in an array
var myFavoriteThings = ['Broccoli', 1024, 'Sherlock'];
myFavoriteThings[0] = 'Asparagus';
Arrays do not have a fixed length. You can use "push" to add something to an array.
var myFavoriteThings = ['Broccoli', 1024, 'Sherlock'];
myFavoriteThings.push('Dancing');
Create an array of your favorite foods. Echo a few values onto your screen.
Use a for loop to easily process each item in an array.
var rainbowColors = ['Red', 'Orange', 'Yellow', 'Green', 'Blue', 'Indigo', 'Violet'];
for (var i = 0; i < rainbowColors.length; i++) {
console.log(rainbowColors[i]);
}
Use a loop to make a list of all your favorite foods.