Mike's JavaScript Crib Sheet

String Methods/Properties: value can be compared to "" for an empty input note that spaces aren't considered to be empty

indexOf( CharToFind, IndexOfStartingChar): returns the index of the first CharToFind that occurs in the string after IndexOfStartingChar, or "-1" if it can't find any more
charAt( Index ): Returns the character at Index in the string
length Property: Number of characters in the string

Function Args:

FunctionName[i]: fetches the ith argument to the function FunctionName Useful for iterating through variable-arg functions
FunctionName.length Property: Returns the number of arguments to the function FunctionName

Using JS to check form inputs

Use the "onClick" event handler to invoke methods that check the values of strings in various form elements, which is good for interactive checking (eg, computing a GPA and returning it to the user)
Use the "onSubmit" event handler in a <FORM> tag to check the input if the onSubmit handler returns "true", then the form is submitted. If the handler returns "false", it isn't
Use the "onLoad" event handler in a ≶BODY> tag to execute code as soon as the page is loaded (for example, setting the focus)

Form Element Methods/Properties