console 命令行工具 X clear

console

let tadom = document.getElementsByTagName('textarea')[0];
let span = document.getElementsByTagName('span')[0];
let regExp = /\n/g;
tadom.addEventListener('input',() => {
    if(tadom.value) {
        span.innerText = 1
        span.innerText = tadom.value.match(regExp).length + 1
    }
})

<textarea></textarea>
<span>0</span>