there is a String (capital S) object wrapper form, typically called a "native," that pairs with the primitive string type; it's this object wrapper that defines the toUpperCase() method on its prototype.

Variables
- An identifier must start with a-z, A-Z, $, or _. It can then contain any of those characters plus the numerals 0-9
- the same rules apply to a property name as to a variable identifier. However, certain words cannot be used as variables, but are OK as property names. These words are called "reserved words," and include the JS keywords (for, in, if, etc.) as well as null, true, and false.
- if you try to access a variable's value in a scope where it's not available, you'll get a ReferenceError thrown. If you try to set a variable that hasn't been declared, you'll either end up creating a variable in the top-level global scope (bad!) or getting an error, depending on "strict mode"
Conditionals
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Javascript Types