Ken McGowan

“Here are the falsy values: false null undefined The empty string '' The number 0 The number NaN All other values are truthy, including true, the string 'false', and all objects.”
― Douglas Crockford, JavaScript: The Good Parts: The Good Parts

“The other form (called for in) enumerates the property names (or keys) of an object. On each iteration, another property name string from the object is assigned to the variable.”
― Douglas Crockford, JavaScript: The Good Parts: The Good Parts

“Names A name is a letter optionally followed by one or more letters, digits, or underbars. A name cannot be one of these reserved words: abstract boolean break byte case catch char class const continue debugger default delete do double else enum export extends false final finally float for function goto if implements import in instanceof int interface long native new null package private protected public return short static super switch synchronized this throw throws transient true try typeof var volatile void while with Most of the reserved words in this list are not used in the language. The list does not include some words that should have been reserved but were not, such as undefined, NaN, and Infinity. It is not permitted to name a variable or parameter with a reserved word. Worse, it is not permitted to use a reserved word as the name of an object property in an object literal or following a dot in a refinement. Names are used for statements, variables, parameters, property names, operators, and labels.”
― Douglas Crockford, JavaScript: The Good Parts: The Good Parts

“When used inside of a function, the var statement defines the function’s private variables.”
― Douglas Crockford, JavaScript: The Good Parts: The Good Parts