无法读取未定义的属性“长度” - JavaScript 中的错误

Question

I am learning animations in html / css / js using a code that reproduces a typewriter effect. Everything is working correctly, but I keep getting this error on my console:

**script.js:33 Uncaught TypeError: Cannot read property 'length' of undefined
at StartTextAnimation (script.js:33)
at script.js:37**

I tried some solutions that I found on google but nothing worked. In my console.log(dataText) each string in my array is executed correctly. The error comes at the moment the loop is executed.

This is the code I'm working on now:

document.addEventListener('DOMContentLoaded', function(event) {
    // array with texts to type in typewriter
    var dataText = ["Cyber", "Sapa", "Synth", "CYBER // SAPA // SYNTH // TÔRTA // POMBADEV.2020"];

    // type one text in the typwriter
    // keeps calling itself until the text is finished
    function typeWriter(text, i, fnCallback) {

        // chekc if text isn't finished yet
        if (i < (text.length)) {
            // add next character to h2
            document.querySelector("h2").innerHTML = text.substring(0, i + 1) + '<span aria-hidden="true"></span>';

            // wait for a while and call this function again for next character
            setTimeout(function() {
                typeWriter(text, i + 1, fnCallback)
            }, 100);
        }
        // text finished, call callback if there is a callback function
        else if (typeof fnCallback == 'function') {
            // call callback after timeout
            setTimeout(fnCallback, 700);
        }
    }
    // start a typewriter animation for a text in the dataText array
    function StartTextAnimation(i) {
        if (typeof dataText[i] == 'undefined') {
            setTimeout(function() {
                StartTextAnimation(0);
            }, 5000);
        }
        // check if dataText[i] exists
        if (i < dataText[i].length) {
            // text exists! start typewriter animation
            typeWriter(dataText[i], 0, function() {
                // after callback (and whole text has been animated), start next text
                StartTextAnimation(i + 1);
            });
        }
    }
    // start the text animation
    StartTextAnimation(0);
});

If anyone can help me I will be very grateful!

PS. Codepen link: https://codepen.io/iMorettini/pen/rNMOvZK

Answer 1

Maybe that dataText[i].length should be dataText.length of your line 33 . Because you are checking for the words, not the letters in the words.

would be helpful if you can post a codepen of your project or something similar.