爲什麼setTimeout（fn，0）有時有用？ - Why is setTimeout(fn, 0) sometimes useful?

問題：

I've recently run into a rather nasty bug, wherein the code was loading a <select> dynamically via JavaScript.我最近遇到了一個非常討厭的錯誤，其中的代碼是通過JavaScript動態加載<select> 。 This dynamically loaded <select> had a pre-selected value.動態加載的<select>具有預先選擇的值。 In IE6, we already had code to fix the selected <option> , because sometimes the <select> 's selectedIndex value would be out of sync with the selected <option> 's index attribute, as below:在IE6中，我們已經有代碼來修復選定的<option> ，因爲有時<select>的selectedIndex值可能與選定的<option>的index屬性不同步，如下所示：

field.selectedIndex = element.index;

However, this code wasn't working.但是，此代碼無法正常工作。 Even though the field's selectedIndex was being set correctly, the wrong index would end up being selected.即使正確設置了字段的selectedIndex ，也將最終選擇錯誤的索引。 However, if I stuck an alert() statement in at the right time, the correct option would be selected.但是，如果我在正確的時間插入了alert()語句，則將選擇正確的選項。 Thinking this might be some sort of timing issue, I tried something random that I'd seen in code before:考慮到這可能是某種時序問題，我嘗試了一些以前在代碼中看到的隨機現象：

var wrapFn = (function() {
    var myField = field;
    var myElement = element;

    return function() {
        myField.selectedIndex = myElement.index;
    }
})();
setTimeout(wrapFn, 0);

And this worked!這有效！

I've got a solution for my problem, but I'm uneasy that I don't know exactly why this fixes my problem.我已經爲我的問題找到了解決方案，但是我不知道自己到底爲什麼能解決我的問題，對此我感到不安。 Does anyone have an official explanation?有人有官方解釋嗎？ What browser issue am I avoiding by calling my function "later" using setTimeout() ?通過使用setTimeout()調用函數“稍後”可以避免出現什麼瀏覽器問題？

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解決方案：

參考一： https://stackoom.com/question/3Gkd
參考二： Why is setTimeout(fn, 0) sometimes useful?