Utilities for safely and unsafely working around TypeScript type checking.

• trySpecify

  • Successful conversion

    const element: HTMLElement = new Image();
    const elementAsImg = trySpecify(element, HTMLImageElement);
    elementAsImg.src = "image.png";

  • Failed conversion

    const element: HTMLElement = new Image();
    // The next function call will throw, because the object stored in element
    // isn't an instance of `HTMLFormElement`
    const elementAsForm = trySpecify(element, HTMLFormElement);
    elementAsForm.method = "post";

• uncheckedCast

  // element1 has type HTMLElement
  const element1 = uncheckedCast<HTMLElement>(document.getElementById("img"));

  function next(val: number) {
    return val + 1;
  }
  
  const str = "hello";
  const nextStr = next(uncheckedCast(str));

• throwIfNull

  // element1 has type HTMLElement | null
  const element1 = document.getElementById("img");
  
  // element2 has type HTMLElement
  const element2 = throwIfNull(document.getElementById("form"));

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