Vanilla JS onclick copy w/ fallback

1) Clipboard API: navigator.clipboard.writeText(text)
Text can be copied to the clipboard directly from a variable.
Only supported on pages served over HTTPS

2) document.execCommand('copy') 👎
Deprecated, but still supported by many browsers

3) Overwrite what is being copied to the clipboard.
element.oncopy=(e)=>{
e.clipboardData.setData('text/plain', text);
e.preventDefault();
};


//Clipboard API with fallback to document.execCommand("copy");

function copyText(text) {
let a;
let textarea= text instanceof HTMLTextAreaElement;
let input= text instanceof HTMLInputElement && text.type == "text";

if(textarea||input){ a= text; }
else{
a= document.createElement("textarea");
a.style.cssText= "opacity:0; pointer-events: none;"
document.body.append(a);
a.value= text;
}

try{
navigator.clipboard.writeText(a.value);
}
catch(x){
a.focus(); a.select();
document.execCommand("copy");
}

if(textarea||input){//Do nothing}
else a.remove();
}

/* Text argument can be a string or a textarea/input element;
let a= document.querySelector("textarea");
let b= "hello";
copyText(a); or copy(b)
*/




//--------------------------------------------





let b= document.querySelector('pre'),
    c= 'i am stupid';

b.addEventListener('copy',
function(e){
e.clipboardData.setData('text', c);
e.preventDefault();
});

b.onclick= function() {
try{ navigator.clipboard.writeText(c);
alert('Copied!');
}
catch(err){
    try{let inp =document.createElement('input');
        document.body.appendChild(inp)
        inp.value= c; inp.select();
        document.execCommand('copy',false);
        inp.remove();
        alert('Copied!!');}
    catch(err){
        try{let e= window.getSelection(),
            f= document.createRange();
            f.selectNodeContents(b);
            e.removeAllRanges();
            e.addRange(f);
            document.execCommand("copy");
            alert('Copied!!!');}
         catch(err){alert("Couldn't copy because: "+ err.message)}
     }
}
};