Make Form Field Random Number Generator Button Disappear When Clicked

I want to incorporate a random number generator into a user form field.

Then... I need the button disappear after it is clicked, so the user can only generate one number.

I have two codes I have been trying to merge, and just can't seem to get it working.

Any guidance in merging the two (or something else) to achieve what I am trying to do would be helpful.

The first code is the Random Number Generator. Which is fine for generating a random number, but I need that number to appear in a form field.

The second code is a basic 'Disappearing Button' code example.

RANDOM NUMBER GENERATOR:

<html>
<body>

<p id="one"></p>

<button onclick="random()";>Generate</button>

<script>

 function random(){

document.getElementById("one").innerHTML = Math.floor(Math.random() * 999999);
}
</script>

</body>
</html>

DISAPPEARING BUTTON CODE:

<script type="text/javascript">

 var Text = 'Random Number';

    function setInput(button) {
       var buttonVal = button.name,
       textbox = document.getElementById('input_' + buttonVal);
       textbox.value = Text ;
       button.style.display = 'none';
    }
</script>

<html>
  
  <input class='input' id="input_a1" name="a1" value="<?php {echo $a1;} ?>"> 
  <input type='submit' name='a1' value='x' onclick='setInput(this); return false;'>
</html>

I tried several things, such as...

<html>
<body>

<p id="one"></p>

<button onclick="random()";>Generate</button>

<script>

 function random(){

document.getElementById("one").innerHTML = Math.floor(Math.random() * 999999);
button.style.display = 'none';
}
</script>

</body>
</html>

No luck. :(

Solution

You can pass this (refers to the element that triggered the event) to random() as an argument called button, then it works fine:

<html>
<body>

<form onsubmit="onSubmit(this, event)">
<p id="one"></p>
<input id="random" name="random" type="hidden">
<button type="button" onclick="generateRandom(this)";>Generate</button>
<button>Submit</button>
</form>

<script>
function generateRandom(button){
  document.getElementById('random').value = document.getElementById("one").innerHTML = Math.floor(Math.random() * 999999);
  button.style.display = 'none';
}
function onSubmit(form, event){
  event.preventDefault();
  console.log(...new FormData(form).entries());
}
</script>

</body>
</html>