javascript - 如何更改文本区域中文本的颜色

Question

我有一个 textarea，当我输入内容时，某些单词的颜色应该会改变。

例如，如果键入的文本是下一个:他去市场买了一个苹果

1. “市场”这个词应该变成绿色
2. “苹果”这个词应该变成红色

这是我当前的代码:

var str = 'market';
var value = str.includes('market');

if (value == str) {
    document.getElementById("text").style.color = "green";
} else {
    document.getElementById("text").style.color = "red";
}

<textarea rows="9" cols="100" id="text" onClick="changeText();"></textarea>

Answer 1

很遗憾，您不能在 textarea 中添加标记, 但这里有一个你可以作为起始方法的想法，它来自这个 link .该方法将基于此:

The basic idea is to carefully position a <div> behind the <textarea>. Then JavaScript will be used to copy any text entered into the <textarea> to the <div>. A bit more JavaScript will make that both elements scroll as one. With everything perfectly aligned, we can add markup inside the <div> to give colors to some particular words, and we going to set text color to transparent on the <textarea>, completing the illusion.

基本实现:

// Initialization.

const colorMap = {"apple": "red", "market": "green", "banana": "orange"};
let textArea = document.getElementById("myTextArea");
let customArea = document.querySelector(".custom-area");
let backdrop = document.querySelector(".backdrop");

// Event listeners.

textArea.addEventListener("input", function()
{
    customArea.innerHTML = applyColors(textArea.value);
});

textArea.addEventListener("scroll", function()
{
    backdrop.scrollTop = textArea.scrollTop;
});

function applyColors(text)
{
    let re = new RegExp(Object.keys(colorMap).join("|"), "gi");

    return text.replace(re, function(m)
    {
        let c = colorMap[m.toLowerCase()];
        return `<spam style="color:${c}">${m}</spam>`;
    });
}

.backdrop, #myTextArea {
  font: 12px 'Open Sans', sans-serif;
  letter-spacing: 1px;
  width: 300px;
  height: 100px;
}

#myTextArea {
  margin: 0;
  position: absolute;
  border-radius: 0;
  background-color: transparent;
  color: transparent;
  caret-color: #555555;
  z-index: 2;
  resize: none;
}

.backdrop {
  position: absolute;
  z-index: 1;
  border: 2px solid transparent;
  overflow: auto;
  pointer-events: none;
}

.custom-area {
  white-space: pre-wrap;
  word-wrap: break-word;
}

<div class="container">
  <div class="backdrop">
    <div class="custom-area">
        <!-- Cloned text with colors will go here -->
    </div>
  </div>
  <textarea id="myTextArea"></textarea>
</div>

请注意，这只是理解基本思想的基本方法。但是通过一些工作，也许你可以获得一个通用版本。例如，到现在为止，textarea无法调整大小。但也许您可以检测到该事件并重新调整 backdrop动态地。