Basic concept of How-JS-Works

Author: lgope

How-JS-Works/Hoisting.js

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+// functions
+calculateAge(1965); // 51
+
+function calculateAge(year) {
+    console.log(2016 - year);
+}
+
+
+// retirement(1956);
+var retirement = function (year) {
+    console.log(65 - (2016 - year));
+}
+
+
+// variables
+console.log(age); // Undefiened
+var age = 23;
+
+function foo() {
+    console.log(age); // Udefined
+    var age = 65;
+    console.log(age); // 65
+}
+
+
+foo();
+console.log(age); // 23

How-JS-Works/Scoping.js

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+// First scoping example
+var a = 'Hello!';
+first();
+
+function first() {
+    var b = 'Hi!';
+    second();
+
+    function second() {
+        var c = 'Hey!';
+        console.log(a + b + c); // Hello!Hi!Hey!
+    }
+}
+
+// Example to show the differece between execution stack and scope chain
+var a = 'Hello!';
+first();
+
+function first() {
+    var b = 'Hi!';
+    second();
+
+    function second() {
+        var c = 'Hey!';
+        third()
+    }
+}
+
+function third() {
+    var d = 'John';
+    // console.log(c); // c is not defined
+    console.log(a + d); // Hello!John
+}

How-JS-Works/This.js

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+// console.log(this); // {}
+calculateAge(1985);
+
+function calculateAge(year) {
+    console.log(2016 - year);
+    console.log(this);
+}
+
+var john = {
+    name: 'John',
+    yearOfBirth: 1990,
+    calculateAge: function () {
+        console.log(this);
+        console.log(2016 - this.yearOfBirth);
+
+        function innerFunction() {
+            console.log(this);
+        }
+        innerFunction();
+    }
+}
+
+john.calculateAge();
+var mike = {
+    name: 'Mike',
+    yearOfBirth: 1984
+};
+
+mike.calculateAge = john.calculateAge; // borrowing calculateAge function from john object
+mike.calculateAge();