Javascript检查IE8中的本机占位符支持 [英] Javascript check for native placeholder support in IE8

问题描述

tldr：
尽管没有对占位符属性的原生支持，为什么（在inputElemnt中''占位符'）在IE8中等于true？不是（元素中的属性）检查本机支持的好方法吗？ Javascript库Modernizer使用它。

tldr: Why does ('placeholder' in inputElemnt) equal true in IE8 despite no native support for the placeholder attribute? Isn't (attribute in element) a good way to check for native support? The Javascript library Modernizer use it.

长：
我有一个名为Defaultvalue的小型Jquery插件（ http://unwrongest.com/projects/defaultvalue/ ）。我有一个名为Placeholder的小Jquery插件（ https://github.com/janjarfalk/jquery.placeholder.js ）。它基本上是HTML5占位符属性的后备。

Long: I have a small Jquery plugin called Defaultvalue ( http://unwrongest.com/projects/defaultvalue/ ). I have a small Jquery plugin called Placeholder ( https://github.com/janjarfalk/jquery.placeholder.js ). It's basically a fallback for the HTML5 placeholder attribute.

在最近的更新中，我添加了这三行代码。希望如果浏览器本身支持占位符属性，则不会运行Defaultvalue。

In a recent updated I added these three lines of code. Hoping that Defaultvalue wouldn't run if the browser had native support for the placeholder attribute.

if('placeholder' in this){
    // this is an input-element
    return false;
}

除IE8和IE7外，它似乎适用于大多数浏览器。由于某种原因，它在此找到了关键的'占位符'，但我认为，IE7 / IE8中没有对占位符属性的任何支持。

It seems to work in most browsers except IE8 and IE7. For some reason it finds the key 'placeholder' in this, but there isn't, I think, any support for the placeholder attribute in IE7/IE8.

我的代码灵感来自Javascript库Modernizer中的此代码（ http://www.modernizr.com/ ）。

My code was inspired by this code in the Javascript library Modernizer ( http://www.modernizr.com/ ).

(function(props) {
    for (var i = 0, len = props.length; i < len; i++) {
        attrs[ props[i] ] = !!(props[i] in inputElem);
    }
    return attrs;
})('autocomplete autofocus list placeholder max min multiple pattern required step'.split(' '));

我缺少什么？

推荐答案

创建一个新的原始输入元素解决了我的问题。

Creating a new raw input element solved my problem.

var nativePlaceholderSupport = (function() {
    var i = document.createElement('input');
    return i.placeholder !== undefined;
})();

if(nativePlaceholderSupport){
    return false;
}

var nativePlaceholderSupport = (function(){
    var i = document.createElement('input');
    return ('placeholder' in i);
})();

if(nativePlaceholderSupport){
    return false;
}

谢谢RobG，你带我去了。

Thanks RobG, you led me to it.

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