Javascript 检查 IE8 中的原生占位符支持
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Javascript check for native placeholder support in IE8
提问by janjarfalk
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.
tldr：尽管没有对占位符属性的本机支持，为什么在 IE8 中 ('placeholder' in inputElemnt) 等于 true？（元素中的属性）不是检查本机支持的好方法吗？Javascript 库 Modernizer 使用它。
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.
长：我有一个名为 Defaultvalue ( http://unwrongest.com/projects/defaultvalue/)的小型 Jquery 插件。我有一个名为 Placeholder ( https://github.com/janjarfalk/jquery.placeholder.js)的小型 Jquery 插件。它基本上是 HTML5 占位符属性的后备。
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.
在最近的更新中，我添加了这三行代码。希望如果浏览器具有对占位符属性的本机支持，则 Defaultvalue 不会运行。
if('placeholder' in this){
// this is an input-element
return false;
}
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.
它似乎适用于除 IE8 和 IE7 之外的大多数浏览器。出于某种原因，它在这里找到了关键的“占位符”，但我认为在 IE7/IE8 中不支持占位符属性。
My code was inspired by this code in the Javascript library Modernizer ( http://www.modernizr.com/).
我的代码的灵感来自 Javascript 库 Modernizer ( http://www.modernizr.com/)中的这段代码。
(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(' '));
What am I missing?
我错过了什么？
采纳答案by janjarfalk
Creating a new raw input element solved my problem.
创建一个新的原始输入元素解决了我的问题。
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;
}
var nativePlaceholderSupport = (function(){
var i = document.createElement('input');
return ('placeholder' in i);
})();
if(nativePlaceholderSupport){
return false;
}
Thanks RobG, you led me to it.
谢谢 RobG，你让我明白了。
回答by ?ime Vidas
It doesn't. It equals to false in both IE9 and IE8.
它没有。它在 IE9 和 IE8 中都等于 false。
Live demo: http://jsfiddle.net/JVSgx/
现场演示：http: //jsfiddle.net/JVSgx/
