# How to JavaScript Part 1

### How to Comment:

• Inline comment
• /Assignment Operator
Initializing Variable with the Assignment Operator

It is common to initialize a variable to an initial value in the same line as it is declared.
var myVar =0;

or

var a = 9;

meaning a = 9

Understanding Uninitialized Variables

### When Javascript declares variables, they have an initial value of undefined. Undefined mathamatical operations result in "NaN" or "Not a number" Here is an example of taking undefined variables to defined. Before: Initialize these three variables var a; var b; var c; Do not change code below this line a = a + 1; b = b + 5; c = c + " String!"; After: Initialize these three variables var a = 5; var b = 10; var c = "I am a" Do not change code below this line a = a + 1; b = b + 5; c = c + " String!"; camelCaseing JavaScript is case sensitive and (Oh crap I probably made a million empty pages on the wiki doing this...) and is really important. Adding/ Subtracting/Multipling and Dividing Numbers Number is a data type in JavaScript which represents numeric data. Use + to add two numbers together (duh?) Add: myVar = 5 + 10; assigned 15 Subtract: var difference = 45 - 33; Multiply: myVar = 13 * 13; assigned 169 Subtract: myVar = 16 / 2; assigned 8 Increment a Number (add one to a number )

Finding a Remainder in JavaScript

### The remainder operator % gives the remainder of the division of two numbers. Example 5 % 2 = 1 because Math.floor(5 / 2) = 2 (Quotient) 2 * 2 = 4 5 - 4 = 1 (Remainder) Usage In mathematics, a number can be checked even or odd by checking the remainder of the division of the number by 2. 17 % 2 = 1 (17 is Odd) 48 % 2 = 0 (48 is Even) Note The remainder operator is sometimes incorrectly referred to as the "modulus" operator. It is very similar to modulus, but does not work properly with negative numbers. var remainder = 11 % 3; Only change code below this line var remainder; Compound Assignment With Augmented Addition

Compound Assignment With Augmented Subtraction

### Like the += operator, -= subtracts a number from a variable. myVar = myVar - 5; will subtract 5 from myVar. This can be rewritten as: myVar -= 5;

Compound Assignment With Augmented Multiplication