So, we can look inside out, not outside in. Two functions declared in the same scope do not have access to anything declared in the other’s scope.
The JavaScript Engine
When our JavaScript code is run in the browser, the JavaScript engine actually makes two separate passes over our code:
Compilation Phase
- variable declaration (allocates memory, sets up reference)
- function declaration
Execution Phase
- actually runs the code! assigning values to variables, invoking functions
Example:
Compilation Phase: a reference to the identifier myVar is stored in memory. The variable isn’t yet assigned a value, and the second line (myVar;) is skipped over entirely because it isn’t a declaration.
Execution Phase: the value 42 is assigned to myVar. When the engine reaches the second line, it sees the identifier myVar and resolves it to a value through a process known as identifier resolution.