代替DOMSubtreeModified实现MutationObserver [英] Implementing MutationObserver in place of DOMSubtreeModified

问题描述

我有一个select[multiple]，我在页面上给出了一个类custom-multiselect，为此，我正在捕获DOMSubtreeModified事件，如下所示:

I have a select[multiple] which I have given a class custom-multiselect on my page for which I am catching the DOMSubtreeModified event as follows:

HTML:

<select class="custom-multiselect"></select>

jQuery:

$('.custom-multiselect').each(function (i, select) {
    var sel = this;
    adjustHeight(sel); //Custom function
    //Binding DOMSubtreeModified to catch if the select list gets modified by the user
    $(sel).on('DOMSubtreeModified', function () {            
        adjustHeight(sel);
    });
    //For Internet Explorer
    $(sel).on('propertychange', function () {
        adjustHeight(sel);
    });
});

这种方法完美无缺.我想将DOMSubtreeModified函数转换为MutationObserver，因为DOMSubtreeModified已贬值.

This approach works flawlessly. I want to convert the DOMSubtreeModified function into MutationObserver since DOMSubtreeModified is depreciated.

所以我做了这样的事情:

So I did something like this:

var observer = new MutationObserver(function (mutation) {
    mutation.forEach(function (m) {
        if (m.type == 'subtree') {
            adjustHeight(this);//Can I use m.target here?
        }
    });
});
observer.observe(document.querySelector('select.custom-multiselect'), {
    subtree: true
});

但是我最终遇到了错误

TypeError:无法将表达式转换为返回指定的类型.

TypeError: The expression cannot be converted to return the specified type.

如何将我的DOMSubtreeModified事件转换为MutationObserver所观察到的?

How can I convert my DOMSubtreeModified event to be observed by the MutationObserver?

推荐答案

• 将代码替换旧的DOM事件，并使用您的sel变量作为观察目标；
• 在MutationObserver中使用childList选项，因为subtree没有指定要查找的内容；
• 由于您只订阅一种类型，因此无需检查突变.
• Put the code in place of the old DOM event and use your sel variable as the observation target;
• Use childList option in MutationObserver because subtree doesn't specify what to look for;
• There's no need to check the mutations since you subscribe only to one type.

$('.custom-multiselect').each(function() {
    var sel = this;
    adjustHeight(sel);

    new MutationObserver(function() {
        adjustHeight(sel);
    }).observe(sel, {childList: true, subtree: true});
});

或者，如果您出于某些原因喜欢.bind:

Or, if you like .bind for some reason:

new MutationObserver(adjustHeight.bind(null, sel))
    .observe(sel, {childList: true, subtree: true});

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