如何使用打字稿找到"placeholder"属性？

Question

如何使用typescript找到html "占位符"属性并在函数中使用该元素?

Answer 1

这个问题很宽泛。例如给定html:

<input placeholder="tada" id="foo"/> 

以下作品:

alert(document.getElementById('foo').getAttribute('placeholder'))

<标题> 更新

修复注释:

$('input[type = "text"][placeholder]')
           .each(function () { 
                    console.log(this.getAttribute('placeholder')); // this is the DOM element
           });

Answer 2

你的HTML输入元素:

<input id='randomId' type='text' val='value' placeholder='This text is just a placeholder!'>

访问元素:

var inputElement = document.getElementById('randomId');

检查浏览器是否支持 javascript中的占位符属性:

// I like having such a simple class ...
var Browser = {
  CanAttribute: function (name) {
    return name in document.createElement('input'); 
  }
}
// ... so you can easily check if your browser supports the placeholder attribute.
if (Browser.CanAttribute('placeholder')) {
}
else {
}

检查是否存在属性:

if ('placeholder' in inputElement) {
  // You can access inputElement.placeholder
}
else {
  // Accessing inputElement.placeholder will throw an ReferenceError-Exception
}

通过javascript检索占位符属性:

var placeholderText = inputElement.placeholder;
console.log(placeholderText); // 'This text is just a placeholder!'

通过javascript设置占位符属性:

inputElement.placeholder = 'This placeholder text overrides the default text!';
console.log(placeholderText); // 'This placeholder text overrides the default text!'