MutationObserver

MutationObserver接口提供了监视对DOM树所做更改的能力。它被设计为旧的Mutation Events功能的替代品，该功能是DOM3 Events规范的一部分。

构造函数

MutationObserver()

创建并返回一个新的 MutationObserver 它会在指定的DOM发生变化时被调用。

方法

disconnect()

阻止 MutationObserver 实例继续接收的通知，直到再次调用其observe()方法，该观察者对象包含的回调函数都不会再被调用。

observe()

配置MutationObserver在DOM更改匹配给定选项时，通过其回调函数开始接收通知。

takeRecords()

从MutationObserver的通知队列中删除所有待处理的通知，并将它们返回到MutationRecord对象的新Array中。

示例

以下示例改编自这篇博客。

// Select the node that will be observed for mutations
var targetNode = document.getElementById('some-id');

// Options for the observer (which mutations to observe)
var config = { attributes: true, childList: true, subtree: true };

// Callback function to execute when mutations are observed
var callback = function(mutationsList) {
    for(var mutation of mutationsList) {
        if (mutation.type == 'childList') {
            console.log('A child node has been added or removed.');
        }
        else if (mutation.type == 'attributes') {
            console.log('The ' + mutation.attributeName + ' attribute was modified.');
        }
    }
};

// Create an observer instance linked to the callback function
var observer = new MutationObserver(callback);

// Start observing the target node for configured mutations
observer.observe(targetNode, config);

// Later, you can stop observing
observer.disconnect();

// ES-next version

// Select the node that will be observed for mutations
let targetNode = document.querySelector(`#id`);

// Options for the observer (which mutations to observe)
let config = {
    attributes: true,
    childList: true,
    subtree: true
};

// Callback function to execute when mutations are observed
const mutationCallback = (mutationsList) => {
    for(let mutation of mutationsList) {
        let type = mutation.type;
        switch (type) {
            case "childList":
                console.log("A child node has been added or removed.");
                break;
            case "attributes":
                console.log(`The ${mutation.attributeName} attribute was modified.`);
                break;
            case "subtree":
                console.log(`The subtree was modified.`);
                break;
            default:
                break;
        }
    }
};

// Create an observer instance linked to the callback function
let observer = new MutationObserver(mutationCallback);

// Start observing the target node for configured mutations
observer.observe(targetNode, config);

// Later, you can stop observing
observer.disconnect();

转自https://developer.mozilla.org/zh-CN/docs/Web/API/MutationObserver