Maybe try adding “window.open(url, ‘_blank’).focus();” in your function blocks.

lnk.href = "https://uk.search.yahoo.com/search?p=" + userInput;
lnk.innerHTML = lnk.href;
window.open(lnk.href, '_blank').focus();
window.location = "https://uk.search.yahoo.com/search?p=" + userInput;

Hard to say, try this and let me know if it works ! ??

The a tag does not work as you are expecting. The a tag is used to encapsulate a link.
What would work for having the effect that you want is to refactor your functions to look like this:

function changeText1(){
    var userInput = document.getElementById('userInput').value;
    var url = "https://www.google.co.uk/search?q=" + userInput ;
    
   window.open(url, '_blank').focus();
}

Using the open method of window

You can follow the examples below: (a, button) tags

document.getElementById('btn').onclick = function () {
   window.open('https://www.google.com', "_blank");
}

<a href="https://www.google.com" target="_blank">Link</a>
</br>
</br>
<button id="btn">button</button>

I am trying to get my code to open a new tab in the browser rather than opening in the same tab, so I added target="_blank" after the href, but this doesn’t work as I don’t think it is being sent.

does anyone know how to fix this code so it works in a new window?

<script>
function changeText1(){
    var userInput = document.getElementById('userInput').value;
    var lnk = document.getElementById('lnk');
    lnk.href = "https://www.google.co.uk/search?q=" + userInput ;
    lnk.innerHTML = lnk.href;
    window.location = "https://www.google.co.uk/search?q=" + userInput;
}
function changeText2(){
    var userInput = document.getElementById('userInput').value;
    var lnk = document.getElementById('lnk');
    lnk.href = "https://www.dogpile.com/serp?q=" + userInput;
    lnk.innerHTML = lnk.href;
    window.location = "https://www.dogpile.com/serp?q=" + userInput;
}
function changeText3(){
    var userInput = document.getElementById('userInput').value;
    var lnk = document.getElementById('lnk');
    lnk.href = "https://uk.search.yahoo.com/search?p=" + userInput;
    lnk.innerHTML = lnk.href;
    window.location = "https://uk.search.yahoo.com/search?p=" + userInput;
}
</script>



<input type='text' id='userInput' value=' ' />
<input type='button' onclick='changeText1()' value='google'/>
<input type='button' onclick='changeText2()' value='Dogpile'/> 
<input type='button' onclick='changeText3()' value='Yahoo'/>
<a href="" target="_blank" id=lnk </a> <br>

I tried adding target to this bit but, it didn’t work.

<a href="" target="_blank" id=lnk </a> <br>