Added more exercises

Author: mattpocock

src/006-expression-of-type-x-cant-be-used-to-index-type-y.problem.ts

@@ -0,0 +1,9 @@
+const productPrices = {
+  Apple: 1.2,
+  Banana: 0.5,
+  Orange: 0.8,
+};
+
+const getPrice = (productName: string) => {
+  return productPrices[productName];
+};

src/006-expression-of-type-x-cant-be-used-to-index-type-y.solution.1.ts

@@ -0,0 +1,14 @@
+const productPrices = {
+  Apple: 1.2,
+  Banana: 0.5,
+  Orange: 0.8,
+};
+
+const getPrice = (productName: keyof typeof productPrices) => {
+  return productPrices[productName];
+};
+
+getPrice("Apple");
+
+// @ts-expect-error
+getPrice("Pear");

src/006-expression-of-type-x-cant-be-used-to-index-type-y.solution.2.ts

@@ -0,0 +1,9 @@
+const productPrices: Record<string, number> = {
+  Apple: 1.2,
+  Banana: 0.5,
+  Orange: 0.8,
+};
+
+const getPrice = (productName: string) => {
+  return productPrices[productName];
+};

src/006-expression-of-type-x-cant-be-used-to-index-type-y.solution.3.ts

@@ -0,0 +1,9 @@
+const productPrices = {
+  Apple: 1.2,
+  Banana: 0.5,
+  Orange: 0.8,
+};
+
+const getPrice = (productName: string) => {
+  return productPrices[productName as keyof typeof productPrices];
+};

src/006-expression-of-type-x-cant-be-used-to-index-type-y.solution.ts

@@ -0,0 +1,3 @@
+class User {
+  private username: string;
+}

src/007-property-x-has-no-initializer-and-is-not-definitely-assigned-in-the-constructor.problem.ts

@@ -0,0 +1,3 @@
+class User {
+  private username: string = "";
+}

src/007-property-x-has-no-initializer-and-is-not-definitely-assigned-in-the-constructor.solution.1.ts

@@ -0,0 +1,7 @@
+class User {
+  private username: string;
+
+  constructor() {
+    this.username = "";
+  }
+}

src/007-property-x-has-no-initializer-and-is-not-definitely-assigned-in-the-constructor.solution.2.ts

@@ -0,0 +1,3 @@
+class User {
+  private username?: string;
+}