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08-advanced-scope.js
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08-advanced-scope.js
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/**
*
* Lexical scope
*
*/
// Think of lexical scope in terms of the compiler
// Decided at compile time, not run time
var teacher = "Kyle";
function otherClass() {
var teacher = "Suzy";
function ask(question) {
console.log(teacher, question);
}
ask("Why");
}
/**
*
* Dynamic scope
*
*/
// Does not exist in Javascript
/**
*
* Function scoping
*
*/
// Use the defensive approach of "minimum exposure"
// Hide things from the global scope as much as possible
/**
*
* IIFE
*
*/
var teacher = "Kyle";
(function anotherTeacher() {
var teacher = "Suzy";
console.log(teacher); // Suzy
})();
console.log(teacher); // Kyle
/**
*
* Block scoping
*
*/
var teacher = "Kyle";
{
let teacher = "Suzy";
console.log(teacher); // Suzy
}
console.log(teacher); // Kyle
/**
*
* let and var
*
*/
function repeat(fn, n) {
var result; // used in the entire function scope
// let for localized usage
for (let i = 0; i < n; i++) {
result = fn(result, i);
}
return result;
}
/**
*
* const
*
*/
const myTeacher = teacher;
myTeacher = "Suzy"; // TypeError
const teachers = ["Kyle", "Suzy"];
teachers[1] = "Brian";
teachers; // [ 'Kyle', 'Brian' ]
/**
*
* Hoisting
*
*/
// variable hoisting is usually bad
teacher = "Kyle";
var teacher;
// function hoisting is pretty useful
getTeacher();
function getTeacher() {
return teacher;
}