@uiw/react-md-editor/esm/utils/InsertTextAtPosition.js

A markdown editor with preview, implemented with React.js and TypeScript.

/**
 * The MIT License
 * Copyright (c) 2018 Dmitriy Kubyshkin
 * Copied from https://github.com/grassator/insert-text-at-cursor
 */
var browserSupportsTextareaTextNodes;
/**
 * @param {HTMLElement} input
 * @return {boolean}
 */

function canManipulateViaTextNodes(input) {
  if (input.nodeName !== 'TEXTAREA') {
    return false;
  }

  if (typeof browserSupportsTextareaTextNodes === 'undefined') {
    var textarea = document.createElement('textarea');
    textarea.value = '1';
    browserSupportsTextareaTextNodes = !!textarea.firstChild;
  }

  return browserSupportsTextareaTextNodes;
}
/**
 * @param {HTMLTextAreaElement|HTMLInputElement} input
 * @param {string} text
 * @returns {void}
 */


export function insertTextAtPosition(input, text) {
  // Most of the used APIs only work with the field selected
  input.focus(); // IE 8-10

  if (document.selection) {
    var ieRange = document.selection.createRange();
    ieRange.text = text; // Move cursor after the inserted text

    ieRange.collapse(false
    /* to the end */
    );
    ieRange.select();
    return;
  } // Webkit + Edge


  var isSuccess = document.execCommand && document.execCommand('insertText', false, text);

  if (!isSuccess) {
    var start = input.selectionStart;
    var end = input.selectionEnd; // Firefox (non-standard method)

    if (typeof input.setRangeText === 'function') {
      input.setRangeText(text);
    } else {
      // To make a change we just need a Range, not a Selection
      var range = document.createRange();
      var textNode = document.createTextNode(text);

      if (canManipulateViaTextNodes(input)) {
        var node = input.firstChild; // If textarea is empty, just insert the text

        if (!node) {
          input.appendChild(textNode);
        } else {
          // Otherwise we need to find a nodes for start and end
          var offset = 0;
          var startNode = null;
          var endNode = null;

          while (node && (startNode === null || endNode === null)) {
            var nodeLength = node.nodeValue.length; // if start of the selection falls into current node

            if (start >= offset && start <= offset + nodeLength) {
              range.setStart(startNode = node, start - offset);
            } // if end of the selection falls into current node


            if (end >= offset && end <= offset + nodeLength) {
              range.setEnd(endNode = node, end - offset);
            }

            offset += nodeLength;
            node = node.nextSibling;
          } // If there is some text selected, remove it as we should replace it


          if (start !== end) {
            range.deleteContents();
          }
        }
      } // If the node is a textarea and the range doesn't span outside the element
      //
      // Get the commonAncestorContainer of the selected range and test its type
      // If the node is of type `#text` it means that we're still working with text nodes within our textarea element
      // otherwise, if it's of type `#document` for example it means our selection spans outside the textarea.


      if (canManipulateViaTextNodes(input) && range.commonAncestorContainer.nodeName === '#text') {
        // Finally insert a new node. The browser will automatically split start and end nodes into two if necessary
        range.insertNode(textNode);
      } else {
        // If the node is not a textarea or the range spans outside a textarea the only way is to replace the whole value
        var value = input.value;
        input.value = value.slice(0, start) + text + value.slice(end);
      }
    } // Correct the cursor position to be at the end of the insertion


    input.setSelectionRange(start + text.length, start + text.length); // Notify any possible listeners of the change

    var e = document.createEvent('UIEvent');
    e.initEvent('input', true, false);
    input.dispatchEvent(e);
  }
}
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