Adding Typewriter Effect via Code Block

Site URL: https://www.wroteon.com/tester

I am trying to inject the code from this article into my own site using a code block. In trying to combine the codes into one and change it to h3 text, I tried the below code, which give the result you can currently see with the dark grey background (please ignore the typewriter effect on the text in the lower section as that is a different approach I am wanting to avoid using):

<h3 id="check">
	I am
	<span id="typewriter"></span>
</h3>

<script>
let data = ["Text1", "Text2","Text3","Text4"];
let len = 0;
let speed=150;
for (let i = 0; i < data.length; ++i) len += 2*data[i].length;
len += 4*data.length;
function type() {
    let p=0;
    for (let i = 0; i < data.length; ++i) {
        let x = 0;
        while (x <= data[i].length) {
            let y=x;
            setTimeout(()=>{
                document.getElementById('typewriter').innerHTML=`${data[i].substr(0,y)}`
            },p*speed)
            ++x,++p;
        }
        --x,p+=2;
        while (x >= 0) {
            let y=x;
            setTimeout(()=>{
                document.getElementById('typewriter').innerHTML=`${data[i].substr(0,y)}`
            },p*speed)
            --x,++p;
        }
    }
    setTimeout(() => {
        type();
    }, len * speed);
}

function blinkingPointer(){
    setTimeout(()=>{
        document.getElementById('check').style.borderRightColor=`red`;
    },500)  
    setTimeout(()=>{
        document.getElementById('check').style.borderRightColor='transparent'
    },1000)  
    setTimeout(()=>{
        blinkingPointer();
    },1000)

}

blinkingPointer();
type();

  #check{
    margin:2px auto;
    width: fit-content;
    border-right: 1px solid;
}
</script>

I have a feeling this has more to do with how I am injecting the code rather than the code itself. 

Thanks for any help you can give!