🗊Презентация Scope in ES3 world. (Lecture 3)

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Lecture III
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Lecture III

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Scope in ES3 world. (Lecture 3), слайд №2
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Scope in ES3 world. (Lecture 3), слайд №3
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Scope in ES3 world. (Lecture 3), слайд №4
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Example
var a = 2;
var b = 2;
console.log(a + b);
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Example var a = 2; var b = 2; console.log(a + b);

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Recap of the previous lecture
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Recap of the previous lecture

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Scope in ES3 World
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Scope in ES3 World

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The Scope of a Variable
The scope of a variable are the locations 
where it is accessible.
 
For example:

function foo() { 
   var x;
}
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The Scope of a Variable The scope of a variable are the locations where it is accessible. For example: function foo() { var x; }

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	Scope - is a logical boundaries in which a variable (or expression) has its meaning. For example, a global variable, a local variable, etc, which generally reflects a logical range of a variable lifetime.
Описание слайда:
Scope - is a logical boundaries in which a variable (or expression) has its meaning. For example, a global variable, a local variable, etc, which generally reflects a logical range of a variable lifetime.

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	Scope - is a logical boundaries in which a variable (or expression) has its meaning. 
	For example, a global variable, a local variable, etc, which generally reflects a logical range of a variable lifetime.
Описание слайда:
Scope - is a logical boundaries in which a variable (or expression) has its meaning. For example, a global variable, a local variable, etc, which generally reflects a logical range of a variable lifetime.

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Scope can be nested
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Scope can be nested

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Nested Scope
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Nested Scope

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Shadowing
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Shadowing

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Shadowing
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Shadowing

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Shadowing
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Shadowing

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Scope in ES3 world. (Lecture 3), слайд №16
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Hoisting
JavaScript hoists all variable declarations, it moves them to the beginning of their direct scopes. 
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Hoisting JavaScript hoists all variable declarations, it moves them to the beginning of their direct scopes. 

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Hoisting
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Hoisting

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Hoisting
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Hoisting

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Only functions introduce new scopes
No block scope
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Only functions introduce new scopes No block scope

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Scope in ES3 world. (Lecture 3), слайд №21
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Scope in ES3 world. (Lecture 3), слайд №22
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Code in global scope
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Code in global scope

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Global namespace
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Global namespace

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Global object (WAT)
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Global object (WAT)

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window vs global
(function (glob) { 
	// glob points to global object 
}(typeof window !== 'undefined' ? window : global));
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window vs global (function (glob) { // glob points to global object }(typeof window !== 'undefined' ? window : global));

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Global variables are evil
They are less robust, behave less predictably, and are less reusable.
Name clashes. Your code, built-ins, analytics code, social media buttons use the same global scope.
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Global variables are evil They are less robust, behave less predictably, and are less reusable. Name clashes. Your code, built-ins, analytics code, social media buttons use the same global scope.

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Globals
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Globals

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Scope in ES3 world. (Lecture 3), слайд №29
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Working with global
window.foo
if (window.foo) { … }
if (“foo” in window) { … }
if (typeof “foo” !== “undefined”) { … }
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Working with global window.foo if (window.foo) { … } if (“foo” in window) { … } if (typeof “foo” !== “undefined”) { … }

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Namespaces
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Namespaces

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immediately invoked function expression
in next lecture
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immediately invoked function expression in next lecture

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REFERENCES
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REFERENCES



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