Added exercises for 02 and 04

Author: mattpocock

src/002-possibly-null-or-undefined.problem.ts

@@ -0,0 +1,5 @@
+const searchParams = new URLSearchParams(window.location.search);
+
+const id = searchParams.get("id");
+
+console.log(id.toUpperCase());

src/002-possibly-null-or-undefined.solution.1.ts

@@ -0,0 +1,5 @@
+const searchParams = new URLSearchParams(window.location.search);
+
+const id = searchParams.get("id");
+
+console.log(id?.toUpperCase());

src/002-possibly-null-or-undefined.solution.2.ts

@@ -0,0 +1,5 @@
+const searchParams = new URLSearchParams(window.location.search);
+
+const id = searchParams.get("id");
+
+console.log(id!.toUpperCase());

src/002-possibly-null-or-undefined.solution.3.ts

@@ -0,0 +1,7 @@
+const searchParams = new URLSearchParams(window.location.search);
+
+const id = searchParams.get("id");
+
+if (id) {
+  console.log(id.toUpperCase());
+}

src/002-possibly-null-or-undefined.solution.4.ts

@@ -0,0 +1,7 @@
+const searchParams = new URLSearchParams(window.location.search);
+
+const id = searchParams.get("id");
+
+if (typeof id === "string") {
+  console.log(id.toUpperCase());
+}

src/002-possibly-null-or-undefined.solution.ts

@@ -0,0 +1,11 @@
+const somethingDangerous = () => {
+  if (Math.random() > 0.5) {
+    throw new Error("Oh dear!");
+  }
+};
+
+try {
+  somethingDangerous();
+} catch (error) {
+  console.log(error.message);
+}

src/004-x-is-of-type-unknown.problem.ts

@@ -0,0 +1,11 @@
+const somethingDangerous = () => {
+  if (Math.random() > 0.5) {
+    throw new Error("Oh dear!");
+  }
+};
+
+try {
+  somethingDangerous();
+} catch (error) {
+  console.log((error as Error).message);
+}

src/004-x-is-of-type-unknown.solution.1.ts

@@ -0,0 +1,15 @@
+const somethingDangerous = () => {
+  if (Math.random() > 0.5) {
+    throw new Error("Oh dear!");
+  }
+};
+
+try {
+  somethingDangerous();
+} catch (error) {
+  if (typeof error === "object" && error && "message" in error) {
+    console.log(error.message);
+  } else {
+    throw error;
+  }
+}

src/004-x-is-of-type-unknown.solution.2.ts

@@ -0,0 +1,15 @@
+const somethingDangerous = () => {
+  if (Math.random() > 0.5) {
+    throw new Error("Oh dear!");
+  }
+};
+
+try {
+  somethingDangerous();
+} catch (error) {
+  if (error instanceof Error) {
+    console.log(error.message);
+  } else {
+    throw error;
+  }
+}