Javascript:如何找到在长段落中选择了特定文本的哪个实例(例如，一个单词在一段中出现多次）

Javascript: How to find which instance of a particular text (e.g. a word which occurs more than once in a paragraph) was selected in a long paragraph?

本文关键字：一个 单词 一段 例如 何找 选择 段落中 文本 实例 Javascript      更新时间：2023-09-26

我计划开发一个web应用程序。在应用程序的一部分中，用户从段落中选择文本，然后单击保存按钮。

例如，用户从以下文本中选择"苹果"（以粗体显示）：

苹果是蔷薇科（蔷薇科）。它是栽培最广泛的树之一果实，以及苹果属众多成员中最广为人知的人类使用的。家苹果树通常被简单地称为苹果树

当用户单击保存按钮时，JS应该将其作为键值对添加到对象中。值应该是所选文本（在这种情况下是apple），而键应该是指示所选文本的哪个实例的东西。原因是"apple"再次出现在给定段落的倒数第二个单词中。

类似于：

var object = new Object();
var textString = window.getSelection().toString();
object.indicator = textString;

我想跟踪用户选择了哪个"苹果"实例（即所选文本）。那么，有可能保留它的踪迹吗

接下来的步骤是存储这个对象，这样当用户再次启动这个页面或回到这里时，我们就会告诉他已经选择了什么。

这个例子没有得到选择了哪个实例（第一个或第二个），但它得到了字符串中的偏移索引，这应该足够了。

<div id="content">An apple is the pomaceous fruit of the Malus domestica tree of the rose family (Rosaceae). It is one of the most widely cultivated tree fruits, and the most widely known of the many members of genus Malus that are used by humans. Malus domestica tree is often simple called as an apple tree.</div>
<button onclick="saveSelection()">Save Selection</button>
<script>
    function saveSelection() {
        var selection = window.getSelection();
        var selectedText = selection.toString();
        var selectionInfo = {
            offset: selection.anchorOffset,
            length: selectedText.length,
            text: selectedText
        };
        localStorage["lastSelection"] = JSON.stringify(selectionInfo);
    }
    window.onload = function () {
        var selectionJSON = localStorage["lastSelection"];
        if (selectionJSON) {
            selection = JSON.parse(selectionJSON);
            alert(JSON.stringify(selection) + "'n" + document.getElementById("content").innerText.substr(selection.offset, selection.length));
        }
    };
</script>

要获取哪个实例，可以使用regex来匹配以前的实例并获取实例的数量。

var text = "An apple is the pomaceous fruit of the Malus domestica tree of the rose family (Rosaceae). It is one of the most widely cultivated tree fruits, and the most widely known of the many members of genus Malus that are used by humans. Malus domestica tree is often simple called as an apple tree.";
var selection = window.getSelection();
var textString = selection.toString();
var previousText = text.substr(0, Math.max(selection.anchorOffset, selection.focusOffset));
//Escape special regex characters, http://stackoverflow.com/a/6969486/3492895
var textRegex = textString.replace(/['-'[']'/'{'}'(')'*'+'?'.'''^'$'|]/g, "''$&");
//Matches all instances, including current one
var instance = previousText.match(new RegExp(textRegex, "g")).length;
alert("Instance: " + instance);

工作示例：http://testnaman.neocities.org/quicktest6.html

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