program.md

Programming With Javascript

Writing a Script

1. Define the Goal
2. Define the task you want to achieve
3. Design the Script
Split the goal into a series of tasks that are going to be involved in solving this puzzle. Can be represented using a flowchart.
4. Code Each Step
Each step needs to be written in a programming language that the computer understands.

Declaring and Calling Functions That Need Info

Sometimes a function needs specific info to perform its task. In such cases, when you declare the function you give it parameters. Inside the function, the parameters act like variables.

function getArea(width, height) {
    return width * height;
}

• width and height are both parameters and usedd like variables within the function

Arguments as Values

getArea(3, 5);

• The function below is called, the number 3 will be used for the width of the wall, and 5 will be used for the height.

Arguments as Variables

wallWidth = 3;
wallHeight = 5;
getArea(wallWidth, wallHeight)

• No need to specify actual valueswhen calling a function - you can use variables in their place.

Getting a Single Value Out of a Function

Some functions return information to the code that called them. For example, when they perform a calculation, they return the result.

function calculateArea(width, height) {
    var area = width * height;
    return area;
}
var wallOne = calculateArea(3, 5);
var wallTwo = calculateArea(8, 5);

Getting a Multiple Values Out of a Function

Functions can return more than one value using an array. For example, this function calculates the area and volume of a box.

functio getSize(width, height, depth) {
    var area = width * height;
    var volume = width * height;
    var sizes = [area, volume];
    return sizes;
}
var areaOne = getSize(3, 2, 3)[0];
var volumeOne = getSize(3, 2, 3)[1];

• areaOne holds the area of a box that is 3 x 2. Area is the first value in the sizes array.
• volumeOne holds the volume of a box that is 3 x 2 x 3. Volume is the second value in the sizes array.

Expressions

An expression evaluates into a single value.

• There are two types of expressions:
  • Expressions that just assign a value to a variable.
    • In order for a variable to be useful it needs a value. This is done using the assignment operator(=).
      • "var color = 'beige';" the value of color is now beige.
    • var is given a special value of undefined. It will change when you assign a value to it.
  • Expressions that use two or more values to return a single value
    • You can perform operations on any number of individual values to determine a single value.
      • "var area =3 * 2;" the value of area is now 6.
    • The expression 3 * 2 evaluates to 6. An assignment operator is used so the result of 3 * 2 is stored in the variable called area.

Operators

Expressions rely on operators; they allow programmers to create a single value from one or more values.

• Assignment Operators
  • color = 'beige'
  • Assigns a value to a variable
• Arithmetic Operators
  • area = 3 * 2
  • Perform basic math
• String Operators
  • Combine two strings
  • greeting = 'Hi' + 'Molly';
• Comparison Operators
  • Compare two values and return true or false
  • buy = 3 > 5;
• Logical Operators
  • Combine expressions and return true or false
  • buy = (5 > 3) && (2 < 4);
    • the value of buy is now true

Arithmetic Operators

Addition (+), adds one value to another, 10+5=15
Subtraction (-), subtracts one value from another, 10-5=5
Division (/), divides two values, 10/5=2
Multiplication (*), multiplies two values, 10*5=50
Increment (++), Adds one to the current number, i=10; 11
                                                i++;
Decrement (--), subtracts one from the current number, i=10; 9
                                                        i--;
Modulus (%), divides two numbers and returns the remainder, 10 % 3 = 1