title: Run time TypeError: input.toLowerCase is not a function
body: <p>While running my <code>react app</code>  I got the error : <code>TypeError: input.toLowerCase is not a function</code>.</p>
  <p>Context: It's a form and I have a textfield inside a controller. Initially the field  id  which I'm working on was <code>string</code> but I needed to change it to <code>number</code>. That's when the type problems started.</p>
  <p>I think the error comes from this line of my code :</p>
  <pre><code>                      inputValue={inputValue as unknown as string}
  
    onInputChange={(_e, newInputValue) =&gt; {
                          setInputValue(parseInt(newInputValue)); //this line
                        }}
  </code></pre>
  <p>using <code>parseInt</code> was the way that I found to get rid of this initial error :</p>
  <pre><code>Argument of type 'string' is not assignable to parameter of type 'SetStateAction&lt;number&gt;'.ts
  </code></pre>
  <p>Any ideas ?</p>