Create closure0.js

Author: dthinkcs

closure0.js

@@ -0,0 +1,94 @@
+// PART 0 
+function instructionGenerator() {
+    function multiplyBy2(num) { // simple declaration just like any other data type
+        return num * 2;
+    }
+    return multiplyBy2;
+}
+
+let generatedFunction = instructionGenerator();
+console.log(generatedFunction(10));
+console.log()
+
+// PART 1.1
+function outer() {
+    let counter = 0;
+    function incrementCounter() {
+        counter++;
+    }
+    incrementCounter();
+}
+
+outer();
+
+// incrementCounter(); // wont work
+
+// PART 1.2 since outhas been popped out then its done(look at the call stack) 
+function funcGenerator() {
+    let counter = 0; // NB: counter now becomes like private access specifier in java coz you can only have getters and setters inside of the function
+    function incrementCounter() {
+        counter++;
+        console.log(counter);
+    }
+    return incrementCounter;
+}
+
+let myNewFunction = funcGenerator(); let func2 = myNewFunction;
+myNewFunction(); // oh oh you can't find counter in the local and then the global...huh we did not get an error
+// BUT BEFORE THAN YOU LOOK IN THE orange box/Bagack 1st before looking at global...Bagpack==LexicalScopeGenerator
+myNewFunction();
+let anotherFunction = func2; //funcGenerator();// myNewFunction;  // IMP funcGenerator makes a new func
+anotherFunction();
+
+
+
+// PART MY 
+function getterFuncGenerator() {
+    let counter = 0;
+    return function () {
+        return counter;
+    }   
+}
+
+function setterFuncGenerator() {
+    let counter = 0;
+    return function(newValue) {
+        counter = newValue;
+        console.log(counter) 
+    }
+}
+
+
+let func1 = setterFuncGenerator();
+func1(10);
+console.log();console.log();console.log();console.log();
+
+function Counter(initialValue=0) {
+    let counter = initialValue;
+    return {
+        getCounter: function () { // getter   COVE->ClosedOverVariableEnvironment
+            return counter;
+        },
+        setCounter: function (newValue) { // setter  COVE->ClosedOverVariableEnvironment
+            counter = newValue;
+        },
+        incrementBy: function (amount) { // method  // COVE->ClosedOverVariableEnvironment
+            counter += amount;
+        }
+    }
+}
+let countObj = Counter();
+console.log(countObj.getCounter());
+countObj.setCounter(10);
+console.log(countObj.getCounter());
+countObj.incrementBy(20);
+console.log(countObj.getCounter());
+
+console.log();
+
+countObj = Counter(100);
+console.log(countObj.getCounter());
+countObj.setCounter(10);
+console.log(countObj.getCounter());
+countObj.incrementBy(20);
+console.log(countObj.getCounter());