将JS函数和事件侦听器应用于多个html元素 [英] Applying JS function and event listener to multiple html elements

问题描述

我正在创建一个表单，下面对此进行了简化，以使您理解到这一点，JS代码是控制占位符；隐藏在焦点上并在模糊时再次出现，显然，这现在仅适用于id('Name')的输入.如何将这些功能应用于所有输入元素DRY，而无需为每个输入重复代码.

I am creating a form which I simplified below to get straight to the point, the JS code is to control the placeholder; hiding on focus and reappear on blur, obviously this now works for the input with id('Name') only. How do I apply these functions to all inputs elements DRY without repeating the code for each input.

var x = document.getElementById("Name");
x.addEventListener("focusin", myFocusFunction);
x.addEventListener("focusout", myBlurFunction);

function myFocusFunction() {
    document.getElementById('Name').placeholder= '';  
}

function myBlurFunction() {
    document.getElementById('Name').placeholder= 'Name';  
}

<div id='card'>
    <input id='Name' type='text' placeholder='Name'/>
    <input id='Age' type='text' placeholder='Age'/>
    <input id='Sex' type='text' placeholder='Sex'/>
    <input id='Occupation' type='text' placeholder='Occupation'/>
</div>

推荐答案

Array.from(document.getElementsByTagName("input")).forEach(input => {

  input.addEventListener("focusin", focus);
  input.addEventListener("focusout", blur.bind(input, input.placeholder));

});


function focus() {
  this.placeholder = '';
}

function blur(placeholder) {
  this.placeholder = placeholder;
}

<div id='card'>
  <input id='Name' type='text' placeholder='Name' />
  <input id='Age' type='text' placeholder='Age' />
  <input id='Sex' type='text' placeholder='Sex' />
  <input id='Occupation' type='text' placeholder='Occupation' />
</div>

使用this关键字，您可以访问触发事件的对象.

Using the this keyword you can access the object which the event was triggered on.

此外，您还需要以某种方式保留占位符，在上面的示例中，我使用了绑定函数，但是您可以选择自己的方式.

Also you need to preserve the placeholder somehow, in the example above I used bound function but you can chose your own way.

您还可以在此答案的版本2 中找到如何手动指定名称的示例.

You can also find an example how to specify names manually in revision 2 of this answer.

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