你可以试试这个:

const wait_until_element_appear = setInterval(() => {
    if ($(element).length !== 0) {
        // some code
        clearInterval(wait_until_element_appear);
    }
}, 0);

这个办法对我很有效

您可以监听DOMNodeInserted或DOMSubtreeModified事件，每当有新元素添加到DOM时，这些事件就会触发。

还有一个LiveQuery jQuery插件，它可以检测创建的新元素:

$("#future_element").livequery(function(){
    //element created
});

如果可以的话，我会尽量避开突变观察者，所以我想到了这个。它看起来类似于上面的一些其他答案。该函数将查找给定DOM调用中存在的第一个元素——className是预期的用法，但它也可以接受tagName或Id。如果您正在寻找具有给定类名或标记名的元素数量，则还可以为精确索引添加参数。

    async function waitUntilElementExits(domkey,domquery,maxtime){
        const delay = (ms) => new Promise(res => setTimeout(res, ms));
        for(let i=0; i<maxtime; i=i+200){
            await delay(200);
            let elm = document[domkey](domquery);
            if( (domkey == 'getElementById' && elm) || elm?.[0] ) break;
        }
    }
    // usage
    await waitUntilElementExits('getElementByClassName','some_class_name',10000)

如果你想让它在一段时间后停止查看(超时)，那么下面的jQuery可以工作。10秒后会暂停。我需要使用这段代码而不是纯JS，因为我需要通过名称选择输入，并且在实现其他一些解决方案时遇到了麻烦。

 // Wait for element to exist.

    function imageLoaded(el, cb,time) {

        if ($(el).length) {
            // Element is now loaded.

            cb($(el));

            var imageInput =  $('input[name=product\\[image_location\\]]');
            console.log(imageInput);

        } else if(time < 10000) {
            // Repeat every 500ms.
            setTimeout(function() {
               time = time+500;

                imageLoaded(el, cb, time)
            }, 500);
        }
    };

    var time = 500;

    imageLoaded('input[name=product\\[image_location\\]]', function(el) {

     //do stuff here 

     },time);

下面的observe函数将允许您通过选择器监听元素。

在下面的例子中，2秒过后，.greeting将被插入到.container中。因为我们正在监听这个元素的插入，所以我们可以有一个在插入时触发的回调。

const observe = (selector, callback, targetNode = document.body) => new MutationObserver(mutations => [...mutations] .flatMap((mutation) => [...mutation.addedNodes]) .filter((node) => node.matches && node.matches(selector)) .forEach(callback)) .observe(targetNode, { childList: true, subtree: true }); const createGreeting = () => { const el = document.createElement('DIV'); el.textContent = 'Hello World'; el.classList.add('greeting'); return el; }; const container = document.querySelector('.container'); observe('.greeting', el => console.log('I have arrived!', el), container); new Promise(res => setTimeout(() => res(createGreeting()), 2000)) .then(el => container.appendChild(el)); html, body { width: 100%; height: 100%; margin: 0; padding: 0; } body { display: flex; } .container { display: flex; flex: 1; align-items: center; justify-content: center; } .greeting { font-weight: bold; font-size: 2em; } <div class="container"></div>

更新

下面是一个实验性的async/await示例。

const sleep = (ms) => new Promise((res) => setTimeout(res, ms)); const observe = (selector, targetNode = document.body) => new Promise(res => { new MutationObserver(mutations => res([...mutations] .flatMap((mutation) => [...mutation.addedNodes]) .find((node) => node.matches && node.matches(selector)))) .observe(targetNode, { childList: true, subtree: true }); }); const createGreeting = () => { const el = document.createElement('DIV'); el.textContent = 'Hello World'; el.classList.add('greeting'); return el; }; const container = document.querySelector('.container'); observe('.greeting', container) .then(el => console.log('I have arrived!', el)); (async () => { await sleep(2000); container.appendChild(createGreeting()); })(); html, body { width: 100%; height: 100%; margin: 0; padding: 0; } body { display: flex; } .container { display: flex; flex: 1; align-items: center; justify-content: center; } .greeting { font-weight: bold; font-size: 2em; } <div class="container"></div>

你也可以使用getElementById代替querySelector

这个函数和 https://stackoverflow.com/a/61511955/10798137

  async function waitForElementById(id, timeout = null, location = document.body) {
    return new Promise((resolve) => {
        let element = document.getElementById(id);
        if (element) {
            return resolve(element);
        }

        const observer = new MutationObserver(async () => {
            let element = document.getElementById(id);
            if (element) {
                resolve(element);
                observer.disconnect();
            } else {
                if (timeout) {
                    async function timeOver() {
                        return new Promise((resolve) => {
                            setTimeout(() => {
                                observer.disconnect();
                                resolve(false);
                            }, timeout);
                        });
                    }
                    resolve(await timeOver());
                }
            }
        });

        observer.observe(location, {
            childList: true,
            subtree: true,
        });
    });

使用它

    waitForElement("tag_id", 500).then((elm) => {
      console.log(elm)
    })

Or

    var elm = async waitForElement("tag_id", 500)