CODE EXAMPLE FOR JAVASCRIPT

input number maxlength

<form method="post">
      <label for="myNumber">My Number:</label>
      <input type="number" maxlength="9" required
      oninput="javascript: if (this.value.length > this.maxLength) this.value = this.value.slice(0, this.maxLength);" >
     <br><br>
      <input type="submit" value="Submit">
</form>