如何从 textarea 中获取突出显示的文本位置？

Question

我想使用 javascript 获取选定的文本位置。例如，
我有一个简单的文本区域。

#input-text {
  resize: none;
  width: 50%;
  height: 50px;
  margin: 1rem auto;
}

<textarea id="input-text">I am a student and I want to become a good person</textarea>

在我的文本区域中，我有一些文本，例如：

"I am a student and I want to become a good person"

从这个字符串中，如果我从 textarea 中选择“成为一个好人”，
那么如何在javascript中获取选定的文本/字符串位置？


这里选择的字符串字符从 29 开始，到 49 结束。所以开始位置是 29，结束位置是 49

Answer 1

这将适用于使用鼠标和键盘对页面上的所有 <textarea> 元素进行文本选择。 如果您不希望所有 <textarea> 元素都有此文本选​​择，请更改选择器（更具体）。

阅读 cmets，如果您不想/不需要键盘选择，您将了解如何禁用键盘选择。

var mySelection = function (element) {
    let startPos = element.selectionStart;
    let endPos = element.selectionEnd;
    let selectedText = element.value.substring(startPos, endPos);

    if(selectedText.length <= 0) {
      return; // stop here if selection length is <= 0
    }
    
    // log the selection
    console.log("startPos: " + startPos, " | endPos: " + endPos );
    console.log("selectedText: " +  selectedText);

  };

var textAreaElements = document.querySelectorAll('textarea');
[...textAreaElements].forEach(function(element) {
    // register "mouseup" event for the mouse
    element.addEventListener('mouseup', function(){
        mySelection(element)
    });
    
    // register "keyup" event for the keyboard
    element.addEventListener('keyup', function( event ) {
        // assuming we need CTRL, SHIFT or CMD key to select text
        // only listen for those keyup events
        if(event.keyCode == 16 || event.keyCode == 17 || event.metaKey) {
            mySelection(element)
        }
    });
});

textarea {
   resize: none; 
   width: 50%;
   height: 50px; 
   margin: 1rem auto;
}

<textarea>I am a student and I want to become a good person</textarea>

Answer 2

我会利用 onselect 事件来获得同样的效果。

<textarea id="input-text" onselect="myFunction(event)">I am a student and I want to become a good person</textarea>


<script>
    function myFunction(event) {
      const start  = event.currentTarget.selectionStart;
      const end= event.currentTarget.selectionEnd;
    }
</script>

Answer 3

Caramba 回答效果非常好，但是我遇到的问题是，如果您选择了一些文本并在文本区域之外释放鼠标 ，则事件不会触发。

为了解决这个问题，我将初始事件更改为mousedown，该事件在文档上注册了一个mouseup 事件，以确保它在释放光标后触发。 mouseup 事件在触发后会自行移除。

这可以通过将once 选项添加到addEventListener 来实现，但遗憾的是IE11 不支持这就是我在sn-p 中使用该解决方案的原因。

var mySelection = function (element) {
    let startPos = element.selectionStart;
    let endPos = element.selectionEnd;
    let selectedText = element.value.substring(startPos, endPos);

    if(selectedText.length <= 0) {
      return; // stop here if selection length is <= 0
    }
    
    // log the selection
    console.log("startPos: " + startPos, " | endPos: " + endPos );
    console.log("selectedText: " +  selectedText);
};

function addSelfDestructiveEventListener (element, eventType, callback) {
    let handler = () => {
        callback();
        element.removeEventListener(eventType, handler);
    };
    element.addEventListener(eventType, handler);
};

var textAreaElements = document.querySelectorAll('textarea');
[...textAreaElements].forEach(function(element) {
    // register "mouseup" event for those
    element.addEventListener('mousedown', function(){
      // This will only run the event once and then remove itself
      addSelfDestructiveEventListener(document, 'mouseup', function() {
        mySelection(element)
      })
    });
    
    // register "keyup" event for the keyboard
    element.addEventListener('keyup', function( event ) {
        // assuming we need CTRL, SHIFT or CMD key to select text
        // only listen for those keyup events
        if(event.keyCode == 16 || event.keyCode == 17 || event.metaKey) {
            mySelection(element)
        }
    });
});

textarea {
   resize: none; 
   width: 50%;
   height: 50px; 
   margin: 1rem auto;
}

<textarea>I am a student and I want to become a good person</textarea>

Answer 4

    var idoftextarea='answer';
    function getSelectedText(idoftextarea){
        var textArea = document.getElementById(idoftextarea);
        var text =textArea.value;
        var indexStart=textArea.selectionStart;
        var indexEnd=textArea.selectionEnd;
        alert(text.substring(indexStart, indexEnd));

    }


    getSelectedText(idoftextarea);

Answer 5

var mySelection = function (element) {
let startPos = element.selectionStart;
let endPos = element.selectionEnd;
let selectedText = element.value.substring(startPos, endPos);

if(selectedText.length <= 0) {
  return; // stop here if selection length is <= 0
}

// log the selection
console.log("startPos: " + startPos, " | endPos: " + endPos );
console.log("selectedText: " +  selectedText); };var textAreaElements = document.querySelectorAll('textarea'); 
[...textAreaElements].forEach(function(element) {
// register "mouseup" event for the mouse
element.addEventListener('mouseup', function(){
    mySelection(element)
});
// register "keyup" event for the keyboard
element.addEventListener('keyup', function( event ) {
    // assuming we need CTRL, SHIFT or CMD key to select text
    // only listen for those keyup events
    if(event.keyCode == 16 || event.keyCode == 17 || event.metaKey) {
        mySelection(element)
    }
});});