javascript - 更改文本背景荧光笔

Question

所以我试图让我的 id="highlighter2" 的每一行的背景颜色 在被点击时有一个黄色背景所以它看起来类似于这个

当它被点击时，该按钮被替换为“Unhighlight them all” 按钮，该按钮取消突出显示所有内容。我尝试使用 ID 定义 onclick，但改为更改背景，正确的做法/方法是什么？

代码:

function Highlighter() {
  var p = document.getElementById("poem"); // get the paragraph
  var p = document.getElementById("highlighter2");
  document.body.style.backgroundColor = "yellow";
}

#poem {
  padding: 10px;
  margin-bottom: 10px;
  color: blue;
  font-size: 1.25em;
  font-family: sans-serif;
  background-color: silver;
  border: 1px dashed black;
  width: 70%;
}

<div id="poem">
  <h2> How Many, How Much </h2>
  <h4> by Shel Silverstein </h4>

  <p id="highlighter2">
    <p> How many slams in an old screen door? </p>
    <p> Depends how loud you shut it.</p>
    <p> How many slices in a bread?</p>
    <p> Depends how thin you cut it.</p>
    <p> How much good inside a day? </p>
    <p> Depends how good you live 'em. </p>
    <p> How much love inside a friend? </p>
    <p> Depends how much you give 'em. </p>
  </p>


</div>

<button type="button" onclick="Highlighter()">Click to highlight</button>
<!-- Highlight -->

Answer 1

Paragraphs: the P element

The P element represents a paragraph. It cannot contain block-level elements (including P itself).

因此，使用一些其他元素来包装所有 p 元素，例如 div。

您可以根据按钮的文本更改背景颜色和文本。

要单独设置所有 p 元素的 backgroundColor，您必须首先定位所有元素。您可以使用 querySelectorAll() 来做到这一点.然后使用 forEach()在 NodeList 上像下面这样:

function Highlighter(btn) {
  var p = document.querySelectorAll('#highlighter2 > p'); // get the paragraph
  if(btn.textContent == 'Click to highlight'){
    p.forEach(function(pEl){
      pEl.style.backgroundColor = "yellow";
    }); 
    btn.textContent = 'Unhighlight them all';
  }
  else{
    p.forEach(function(pEl){
      pEl.style.backgroundColor = "";
    });
    btn.textContent = 'Click to highlight';
  }
}

#poem {
  padding: 10px;
  margin-bottom: 10px;
  color: blue;
  font-size: 1.25em;
  font-family: sans-serif;
  background-color: silver;
  border: 1px dashed black;
  width: 70%;
}

<div id="poem">
  <h2> How Many, How Much  </h2>
  <h4> by Shel Silverstein </h4>

  <div id="highlighter2">
    <p> How many slams in an old screen door? </p>
    <p> Depends how loud you shut it.</p>
    <p> How many slices in a bread?</p>
    <p> Depends how thin you cut it.</p>
    <p> How much good inside a day? </p>
    <p> Depends how good you live 'em. </p>
    <p> How much love inside a friend? </p>
    <p> Depends how much you give 'em. </p>
  </div>


</div>

<button type="button" onclick="Highlighter(this)">Click to highlight</button><!-- Highlight -->