通过api调用在值更改时自动调整文本区域的大小（纯JavaScript）

Question

我正在尝试在textarea上添加自动调整大小功能。 仅当我键入某些内容时，下面的代码才能很好地工作。 但是，如果我只是更新api中的值，则不会触发任何事件。 因此，无法调整大小。 无论如何，我可以触发键盘输入或其他事件来触发函数以编程方式获取scrollHeight吗？

autoResizeTextArea = (e) => {
  const element = e.target
  element.style.height = 'auto'
  element.style.overflowY = 'hidden'
  element.style.height = element.scrollHeight + 'px'
}

Answer 1

如果您控制更改代码的JavaScript库，则只需调用element.onchange()即可手动触发事件element.onchange()

UPDATE

并且不要忘记将事件侦听器onchange附加到您的元素

请注意，应通过html指令通过js element.onchange进行设置。

这是一个工作示例jsfiddle

HTML：

<textarea id="mytext"></textarea>
<button id="mybtn">change input</button>

JS：

var onChange = function(){
    alert('input changed');
}

var changeInput = function(){
  text.value = 'Hello World';
    text.onchange();
}

button = document.getElementById('mybtn');
button.onclick = changeInput;

text = document.getElementById('mytext');
text.onchange = onChange; 

Answer 2

https://jsfiddle.net/ab9hkbL7/1/

let textarea = document.querySelector("#myTextArea");
let tael = textarea.addEventListener.bind(textarea);

let autoResizeTextArea = (e) => {
  const element = e.target
  element.style.height = 'auto'
  element.style.overflowY = 'hidden'
  element.style.height = element.scrollHeight + 'px'
}

tael('update', autoResizeTextArea);
tael('keyup', autoResizeTextArea);
//add event listeners for update and keyup

//for demonstration set value big enough that it will resize box:
textarea.value = `lorem Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.`;

//setup promise to resolve after 2 seconds. 
//This will simulate fetching external data.

let newPromise = new Promise((res, rej) => {
  setTimeout(() => {
    res('resolved');
  }, 2000)
}).then((success) => {

//create the update event and dispatch it
  let myEvent = new CustomEvent("update");
  textarea.dispatchEvent(myEvent);
});

有关更多信息，请查看MDN： dispatchEvent CustomEvent