How to Determine the Word Under the Cursor in JavaScript?

Determining the Word Under the Cursor in JavaScript

Problem:

Given an HTML page containing text, how can you determine the word that the cursor is currently hovering over?

Solution:

For Browsers that Support Shadow DOM (e.g., Chrome)

<code class="js">function getWordAtPoint(elem, x, y) {
  if (elem.nodeType === elem.TEXT_NODE) {
    // Create a range encompassing the element and determine offsets
    let range = elem.ownerDocument.createRange();
    range.selectNodeContents(elem);
    let currentPos = 0;
    let endPos = range.endOffset;

    // Iterate through the characters until finding the one under the cursor
    while (currentPos + 1 < endPos) {
      range.setStart(elem, currentPos);
      range.setEnd(elem, currentPos + 1);
      let boundingClientRect = range.getBoundingClientRect();

      if (
        boundingClientRect.left <= x &&
        boundingClientRect.right >= x &&
        boundingClientRect.top <= y &&
        boundingClientRect.bottom >= y
      ) {
        // Expand to word boundaries and return the text
        range.expand("word");
        let result = range.toString();
        range.detach();
        return result;
      }

      currentPos += 1;
    }
  } else {
    // Recursively check child nodes
    for (let i = 0; i < elem.childNodes.length; i++) {
      range = elem.childNodes[i].ownerDocument.createRange();
      range.selectNodeContents(elem.childNodes[i]);

      // Check if child node is under the cursor
      if (
        range.getBoundingClientRect().left <= x &&
        range.getBoundingClientRect().right >= x &&
        range.getBoundingClientRect().top <= y &&
        range.getBoundingClientRect().bottom >= y
      ) {
        range.detach();
        // Recursively search the child node
        return getWordAtPoint(elem.childNodes[i], x, y);
      } else {
        range.detach();
      }
    }
  }

  return null;
}</code>

Example Usage:

<code class="js">document.addEventListener("mousemove", (e) => {
  let word = getWordAtPoint(e.target, e.x, e.y);
  console.log("Word under cursor:", word);
});</code>

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