# document.write(crsNum);/Resources

## JavaScript Cheat Sheet

• Variables:
• Variables are containers for storing data values.
• Arithmetic: `+ - * / %`
• `%` is for modulo. Modulo returns the remainder after integer division. For example `17 % 7` results in `3` since 17 divided by 7 has a remainder of 3.
• Math Functions:
• `Math.PI`
• `Math.round()`
• `Math.round( x )` returns the value of `x` rounded to its nearest integer.
• `Math.ceil( x )` returns the value of `x` rounded up to the nearest integer.
• `Math.floor( x )` returns the value of `x` rounded down to the nearest integer.
• `Math.pow()`
• `Math.pow( x, y )` returns the value of `x` to the power of `y`.
• `Math.sqrt()`
• `Math.sqrt( x )` returns the square root of `x`.
• `Math.random()`
• Returns a random number between `0` (inclusive), and `1` (exclusive).
• Types and Type Casting: `number`, `string`, `boolean`
• `typeof( x )`
• Returns the type name of `x` as a string.
• `Number( x )`
• A function that converts strings to numbers.
• `Number( "3" )` returns `3`
• `Number( "John" )` returns `NaN` (Not A Number)
• `String( x )`
• Converts the value of `x` into a string.
• `String( 45 )` converts the number `45` into the string `"45"`
• `String( true )` converts the boolean `true` into the string `"true"`
• Strings:
• `+`
• Concatenates two strings (puts them together into one string)
• Example: `"Go " + "Navy"` evaluates to `"Go Navy"`
• `x.length`
• Returns the length of string `x`.
• `'Hello'.length` returns `5`
• `x.charAt( y )`
• Returns the character at position `y` in string `x`.
• Indexing starts at `0`.
• `'Hello'.charAt( 1 )` returns `"e"`
• `x.charCodeAt( y )`
• Returns the ASCII decimal value of the character at position `y` in string `x`.
• `"Hello".charCodeAt( 1 )` returns `101`
• `String.fromCharCode( x )`
• Returns a string consisting of the ASCII character represented by the decimal value `x`.
• Input and Output:
• `alert( x )` (Output)
• Displays a popup window with the value of `x`.
• E.g. `alert("Hello World!");`
Produces a popup window that says `Hello World!`
• `prompt( x )` (Input)
• Produces a popup window with the value of `x` with a text box for the user to enter a value.
• Returns a string of what the user entered into the text box.