code

4-sophisticated-type-manipulation/4-2-using-type-assertion/exampleJsonString.ts

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+let jsonString: string = '{"name": "John", "age": 30}';
+
+// We know the structure of JSON, assert the type
+let userInfo: { name: string; age: number } = JSON.parse(jsonString) as { name: string; age: number };
+
+console.log(userInfo.name); // Outputs: John
+console.log(userInfo.age); // Outputs: 30

4-sophisticated-type-manipulation/4-2-using-type-assertion/usingTypeAssertion.ts

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+let someValue: any = "this is a string";
+
+let strLength: number = (someValue as string).length;
+
+console.log(strLength); // Outputs the length of "someValue"
+
+let someValue2: any = "this is another string";
+
+let strLength2: number = (<string>someValue).length;
+
+console.log(strLength2); // Outputs the length of "someValue"