您不能在textarea中进行更改，因为textarea仅包含纯文本，要为找到的单词添加格式，您需要将这些匹配的单词括起来html元素中的单词，因此这就是为什么它不起作用的原因，例如 JSFiddle ，这是另一种实现方式，如果您在搜索框中使用空格将多个单词分隔，例如item1 item item3:

You can't change it in a textarea because textarea only contains pure text, to add format to words yo ufound you need to surround these matched words within html elements, so this why it won't work, as in this JSFiddle, just another way of doing it, you can search for multiple words if you separate them by a space in the search box like item1 item item3:

var div = $('#text'), kw,keywords, i, j;
$('#btn').on('click', function (event) {
    event.preventDefault();
    console.clear();
    kw = $('#keywords').val();
    keywords = kw.split(" ");
    text = div.text();
    text = text.replace(/,|\.|\?/i, "");
    text = text.split(" ");
    for (i = 0; i < text.length; i++) {
        for (j = 0; j < keywords.length; j++) {
            if (text[i] == keywords[j]) {
                text[i] = '<span class="hl">' + text[i] + '</span>';
            }
        }
    }
    text = text.join(" ");
    div.html(text);
});

div {
    width:400px;
    height:250px;
    display:block;
    overflow:hidden;
    border:lightgrey 2px inset;
    padding:1px;
    overflow:hidden;
    overflow-y:scroll;
}
.hl{
    background-color:orange;
    padding:2px 3px;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.0/jquery.min.js"></script>
<form name="form">
    <input id="keywords" type="text" value="">
    <input id="btn" type="submit" value="Search">
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</form>