JavaScript_Succinctly

Chapter 13 Scope and Closures
Conceptual overview of JavaScript scope
In JavaScript, scope is the context in which code is executed. There are three types of
scope: global scope, local scope (sometimes referred to as "function scope"), and eval
scope.
Code defined using var inside of a function is locally scoped, and is only "visible" to
other expressions in that function, which includes code inside any nested/child
functions. Variables defined in the global scope can be accessed from anywhere
because it is the highest level and last stop in the scope chain.
Examine the code that follows and make sure you understand that each declaration of
foo is unique because of scope.
Sample: sample110.html
var foo = 0; // Global scope.
console.log(foo); // Logs 0.
var myFunction = function () {
var foo = 1; // Local scope.
console.log(foo); // Logs 1.
var myNestedFunction = function () {
var foo = 2; // Local scope.
console.log(foo); // Logs 2.
} ();
} ();
eval('var foo = 3; console.log(foo);'); // eval() scope.
Make sure you understand that each foo variable contains a different value because
each one is defined in a specifically delineated scope.
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