这里有一个使用可观测数据的解决方案。

waitForElementToAppear(elementId) {                                          

    return Observable.create(function(observer) {                            
            var el_ref;                                                      
            var f = () => {                                                  
                el_ref = document.getElementById(elementId);                 
                if (el_ref) {                                                
                    observer.next(el_ref);                                   
                    observer.complete();                                     
                    return;                                                  
                }                                                            
                window.requestAnimationFrame(f);                             
            };                                                               
            f();                                                             
        });                                                                  
}                                                                            

现在你可以写

waitForElementToAppear(elementId).subscribe(el_ref => doSomethingWith(el_ref);

这是一种纯粹的基于承诺的JavaScript方法，您可以知道需要等待多少毫秒。

    const waitElementFor = function(query, ms = 3000) { // 3000 === 3 seconds
        return new Promise((resolve) => {
            var waited = 0;
            var el = null;
            var wi = setInterval(function() {
                el = document.querySelector(query);
                if (waited >= ms || el) {
                    clearInterval(wi);
                    if(el) {
                        resolve(el);
                    } else {
                        resolve(null);
                    }
                }
                waited += 10;
            }, 10);  
        });
    }

要使用该函数，只需在异步函数中使用以下代码。

var element = await waitElementFor('#elementID');

代码片段:

const waitElementFor = function(query, ms = 3000) { // 3000 === 3 seconds return new Promise((resolve) => { var waited = 0; var el = null; var wi = setInterval(function() { el = document.querySelector(query); if (waited >= ms || el) { clearInterval(wi); if(el) { resolve(el); } else { resolve(null); } } waited += 10; }, 10); }); } async function snippetTestAyncFunction(){ var element = await waitElementFor('#elementID'); console.log(element); } snippetTestAyncFunction();

在requestAnimationFrame中中继比在setTimeout中更好。这是我在es6模块和使用承诺的解决方案。

Es6、模块和承诺:

// onElementReady.js
const onElementReady = $element => (
  new Promise((resolve) => {
    const waitForElement = () => {
      if ($element) {
        resolve($element);
      } else {
        window.requestAnimationFrame(waitForElement);
      }
    };
    waitForElement();
  })
);

export default onElementReady;

// in your app
import onElementReady from './onElementReady';

const $someElement = document.querySelector('.some-className');
onElementReady($someElement)
  .then(() => {
    // your element is ready
  }

纯js和承诺:

var onElementReady = function($element) {
  return new Promise((resolve) => {
    var waitForElement = function() {
      if ($element) {
        resolve($element);
      } else {
        window.requestAnimationFrame(waitForElement);
      }
    };
    waitForElement();
  })
};

var $someElement = document.querySelector('.some-className');
onElementReady($someElement)
  .then(() => {
    // your element is ready
  });

这是对杰米·哈伯的回答的一个小小的改进

const checkElement = async selector => {
  while ( document.querySelector(selector) === null) {
    await new Promise( resolve =>  requestAnimationFrame(resolve) )
  }
  return document.querySelector(selector); 
};

使用方法:

checkElement('.myElement').then((selector) => {
  console.log(selector);
});

如果你想要一个通用的MutationObserver解决方案，你可以使用这个函数

// MIT Licensed
// Author: jwilson8767

/**
 * Waits for an element satisfying selector to exist, then resolves promise with the element.
 * Useful for resolving race conditions.
 *
 * @param selector
 * @returns {Promise}
 */
export function elementReady(selector) {
  return new Promise((resolve, reject) => {
    const el = document.querySelector(selector);
    if (el) {resolve(el);}
    new MutationObserver((mutationRecords, observer) => {
      // Query for elements matching the specified selector
      Array.from(document.querySelectorAll(selector)).forEach((element) => {
        resolve(element);
        //Once we have resolved we don't need the observer anymore.
        observer.disconnect();
      });
    })
      .observe(document.documentElement, {
        childList: true,
        subtree: true
      });
  });
}

来源:https://gist.github.com/jwilson8767/db379026efcbd932f64382db4b02853e 如何使用它的例子

elementReady('#someWidget').then((someWidget)=>{someWidget.remove();});

注意:MutationObserver有很好的浏览器支持;https://caniuse.com/#feat=mutationobserver

voila !：）

您可以通过设置超时来检查dom是否已经存在，直到它已经在dom中呈现。

var panelMainWrapper = document.getElementById('panelMainWrapper');
setTimeout(function waitPanelMainWrapper() {
    if (document.body.contains(panelMainWrapper)) {
        $("#panelMainWrapper").html(data).fadeIn("fast");
    } else {
        setTimeout(waitPanelMainWrapper, 10);
    }
}, 10);