TypeScript Temporal Uncertainty

TypeScript-Temporal-Uncertainty.ts

let displayNames = ['Joe Doe', 'Jane Doe'];
const getSuffix = () => {
    if (Math.random() * 100 < 50) {
      return null;
    }
    return 'md';
  };

  displayNames.forEach((name) => {
    let suffix = getSuffix();
      /*The challenge is that TypeScript allows for both Async and Sync execution. Since TypeScript often errs on the side of Type-Safety and in the case of Async has no guarantee of what a value will be at execution, you can get a Type Error that you know is not correct (code below-showing error even after a NULL check). A solution is to save the value to a local variable. This assures TypeScript of Type at execution and there is no longer a Type Error given.*/
    if (suffix != null) {
      const suffixLocal = suffix; // prevents Type Error
      setTimeout(() => {
        name += ', ' + suffixLocal.toUpperCase();
        console.log({ name });
      },100);
    }
    suffix = null;
  });