问如何让KeyboardEvents更改HTMLInputElement的值？

EN

    function setupTest(elem) {
      const input = elem[0] as HTMLInputElement;
      const letters = "aSdFgH";
      let index = 0;

      $("#injectButton").click(() => {
        const char = letters.charAt(index);
        const keydown = new KeyboardEvent("keydown", {
            key: char,
            shiftKey: char >= 'A' && char <= 'Z'
        });

        const keyup = new KeyboardEvent("keyup", {
            key: char,
            shiftKey: char >= 'A' && char <= 'Z'
        });
        index++;
        input.dispatchEvent(keydown);
        input.dispatchEvent(keyup);
    });

    const report = (name, event) => {
        const target = event.target as HTMLInputElement;
        console.log(name, target.value, event);
    }

    $(elem)
        .focus(event => report("FOCUS", event))
        .keydown(event => report("KEYDOWN", event))
        .keyup(event => report("KEYUP", event))
        .blur(event => report("BLUR", event))
    ;
}