JavaScript Typing Effect Function-CodePudding

I'm trying to write a JS function that takes one argument, txt and prints it letter by letter, I already have a code, but when I try to 'convert' it as a function it stops working. Any ideas?

var myText = "Text to be displayed";    
var myArray = myText.split("");    
var loopTimer;

function frameLooper() {    
    if(myArray.length > 0) {    
        document.getElementById("type_text").innerHTML  = myArray.shift();    
    } else {
        clearTimeout(loopTimer);
        return false;
    }
    loopTimer = setTimeout("frameLooper()",70);
}
frameLooper();

Typing effect function:

var i;
var speed = 120;

function typeWriter(txt) {
  for (i=0;i<=txt.length - 1;i  )
  {
    document.getElementById("type_text").innerHTML  = txt.charAt(i);
    setTimeout(typeWriter, speed);
  }
}
typeWriter("text to be typed");

CodePudding user response：

You need to pass the original text to the function in setTimeout, as well as remove the loop over the entire text, that you are calling in each setTimeout callback (which makes it print the entire text in each callback).

As an enhancement, I would suggest passing the index in the function calls as well.

const SPEED = 120;

function typeWriter(txt, i = 0) {
  document.getElementById("type_text").innerHTML  = txt.charAt(i);
  
  // check if the entire text has been typed
  if (i < txt.length - 1) {
    // pass function with the text and the index ( 1)
    setTimeout(() => typeWriter(txt, i   1), SPEED);
  }
}
typeWriter("text to be typed");

<p id="type_text"></p>

CodePudding user response：

It's easier with promises and async:

let delay = n => new Promise(r => setTimeout(r, n));

async function typeWriter(div, txt) {
  for (let char of txt) {
    div.innerHTML  = char;
    await delay(200);
  }
}

typeWriter(document.querySelector('#type'), 'hello there')

<div id="type"></div>