AddEventListener is not a function appears in js

AddEventListener is not a function appears in js

textarea.addEventListener is not a function

Business scenario:
https://juejin.cn/post/6978721383983530015

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Error screenshot:

Cause Analysis:

js addEventListener is not a function, most likely the event source of the listening event is incorrect, and the event source should be an element, not an array.

getElementsByClassName, getElementByTagName()all obtained are arrays, even if there is only one element that satisfies the condition, it is still an array.
Therefore, when listening to events, [0] must be added, otherwise the following error will be reported

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Solution:

// autoHeightTextarea();//textarea 自动撑高
    var textarea = document.getElementsByClassName('autoh');
    textarea[0].addEventListener('input', (e) => {
    
    
        textarea[0].style.height = '180px';
        textarea[0].style.height = e.target.scrollHeight + 'px!important';
        // console.log(e);
    });

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Reference article:
https://blog.csdn.net/weixin_47417033/article/details/124261891