complete ts chapter - 5

Author: jinnatul

README.md

@@ -6,7 +6,7 @@
 | 2: Why and when to use TypeScript | [Readme](/chapters/2/readme.md) |
 | 3: TypeScript Core Types | [Readme](/chapters/3/readme.md) |
 | 4: Arrays | [Readme](/chapters/4/app.ts) |
-| 5: Enums | [Readme]() |
+| 5: Enums | [Readme](/chapters/5/readme.md) |
 | 6: Functions | [Readme]() |
 | 7: Classes | [Readme]() |
 | 8: Class Decorator | [Readme]() |

chapters/5/codes/5.1/app.ts

@@ -0,0 +1,39 @@
+/*
+By default all enum values are resolved to numbers. Let's say if you have something 
+like
+
+*/
+enum myEnum {
+  JPEG,
+  PNG,
+  PDF
+}
+console.log(myEnum.PDF); // 2
+
+enum myEnumLink {
+  JPEG = <any>'image/jpeg',
+  PNG = <any>'image/png',
+  PDF = <any>'application/pdf'
+}
+console.log(myEnum.PNG); // 1
+
+enum myEnumOnlyLink {
+  JPEG = 'image/jpeg',
+  PNG = 'image/png',
+  PDF = 'application/pdf',
+}
+console.log(myEnum.JPEG); // 0
+
+enum MyType {
+  Value = 3,
+  ValueEx = 30,
+  ValueEx2 = 300
+}
+console.log(MyType.ValueEx); // 30
+
+enum FancyType {
+  OneArr = <any>[1],
+  TwoArr = <any>[2, 2],
+  ThreeArr = <any>[3, 3, 3]
+}
+console.log(FancyType.ThreeArr); // [ 3, 3, 3 ]

chapters/5/codes/5.2/app.ts

@@ -0,0 +1,18 @@
+enum SomeEnum { A, B };
+
+console.log(SomeEnum); // { '0': 'A', '1': 'B', A: 0, B: 1 }
+
+let enumValues:Array<string> = [];
+for(let value in SomeEnum) {
+  if(typeof SomeEnum[value] === 'number') {
+    enumValues.push(value);
+  }
+}
+
+console.log(enumValues); // [ 'A', 'B' ]
+
+enumValues.forEach(v=> console.log(v));
+/*
+A
+B
+*/

chapters/5/codes/5.3/app.ts

@@ -0,0 +1,33 @@
+enum SourceEnum {
+  value1 = <any>'value1',
+  value2 = <any>'value2'
+}
+  
+enum AdditionToSourceEnum {
+  value3 = <any>'value3',
+  value4 = <any>'value4'
+}
+
+
+// we need this type for TypeScript to resolve the types correctly
+type TestEnumType = SourceEnum | AdditionToSourceEnum;
+// and we need this value "instance" to use values
+let TestEnum = Object.assign({}, SourceEnum, AdditionToSourceEnum);
+// also works fine the TypeScript 2 feature
+// let TestEnum = { ...SourceEnum, ...AdditionToSourceEnum };
+
+console.log(TestEnum);
+
+function check(test: TestEnumType) {
+  return test === TestEnum.value2;
+}
+
+console.log(TestEnum.value1);
+console.log(TestEnum.value2 === <any>'value2');
+console.log(check(TestEnum.value2));
+console.log(check(TestEnum.value3));
+
+/******** 
+ * Some how there have a bit error 
+ * Object.assign not support there
+ * **********/

chapters/5/codes/5.4/app.ts

@@ -0,0 +1,33 @@
+class Enum {
+  constructor(protected value: string) {}
+  public toString() {
+    return String(this.value);
+  }
+
+  public is(value: Enum | string) {
+    return this.value = value.toString();
+  }
+}
+
+class SourceEnum extends Enum {
+  public static value1 = new SourceEnum('value1');
+  public static value2 = new SourceEnum('value2');
+}
+
+class TestEnum extends SourceEnum {
+  public static value3 = new TestEnum('value3');
+  public static value4 = new TestEnum('value4');
+}
+
+function check(test: TestEnum) {
+  return test === TestEnum.value2;
+}
+
+let value1 = TestEnum.value1;
+
+console.log(value1 + ' hello'); // value1 hello
+console.log(value1.toString() === 'value1'); // true
+console.log(value1.is('value1')); // value1
+console.log(!TestEnum.value3.is(TestEnum.value3)); // false
+console.log(check(TestEnum.value2)); // true
+console.log(TestEnum.value1 == <any>'value1'); // true

chapters/5/readme.md

@@ -0,0 +1,8 @@
+# Enums
+
+| **Topic** | **Code** |
+|:---------:|:--------:|
+| Section 5.1: Enums with explicit values | [code-here](/chapters/5/codes/5.1/app.ts) |
+| Section 5.2: How to get all enum values | [code-here](/chapters/5/codes/5.2/app.ts) |
+| Section 5.3: Extending enums without custom enum implementation | [code-here](/chapters/5/codes/5.3/app.ts) |
+| Section 5.4: Custom enum implementation: extends for enums | [code-here](/chapters/5/codes/5.4/app.ts) |