Is there a way to assign the user's input and/or selection into the message?

Question

<input type="radio" name="T" id="twenT">20
<input type="radio" name="T" id="sixT">60
<input id="uIn"></input>
<a href="sms://+15552345678;?&body=CHANGE%20THIS"></a>
<button onclick="function()">

How do I make it so that the user selects one option or inputs text and then the text message changes to the text that was selected/entered. Pure JavaScript is preferred.

Answer 1

Try this

I changed to name="T" to make them valid radios

I also closed the A to make it valid. If you want to click the link and change, then we can remove the button

const href = "sms://+15552345678;?&body="
const sms = document.getElementById("sms");
const uIn = document.getElementById("uIn");
document.getElementById("changeMsg").addEventListener("click",function(e) {
  const val = document.querySelector("input[name=T]:checked");
  if (val) {
    sms.href = href.split("body=")
      .join(`body=${encodeURIComponent(val.value)}&uIn=${encodeURIComponent(uIn.value)}`)
    console.log(sms.href)
  }  
  else {
    console.log("radio not checked")
  }
})

<input type="radio" name="T" value="twenT">20
<input type="radio" name="T" value="sixT">60
<input id="uIn" type="text" value="" />
<a id="sms" href="sms://+15552345678;?&body=CHANGE%20THIS">Call us</a>
<button id="changeMsg" type="button">Change</button>