TextUpdateEvent: selectionStart property

Limited availability

This feature is not Baseline because it does not work in some of the most widely-used browsers.

Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The TextUpdateEvent.selectionStart read-only property indicates the position of the end of the selection (or caret) within the text content of the editable region attached to the EditContext object.

Value

Examples

Using textupdate to render the edited text and user selection

This example shows how to use the selectionStart property to render the selected text within a textupdate event handler.

css
#editor {
  height: 200px;
  background: #eee;
  color: black;
}

.selection {
  display: inline-block;
  vertical-align: bottom;
  background: blue;
  color: white;
  min-width: 2px;
  height: 3ex;
}
html
<div id="editor"></div>
js
const editorEl = document.getElementById("editor");
const editContext = new EditContext();
editorEl.editContext = editContext;

editContext.addEventListener("textupdate", (e) => {
  // Clear the current content.
  editorEl.innerHTML = "";

  const text = editContext.text;
  const { selectionStart, selectionEnd } = e;

  // Render the text before the selection.
  const textBefore = document.createElement("span");
  textBefore.textContent = text.substring(0, selectionStart);

  // Render the selected text, or caret.
  const textSelected = document.createElement("span");
  textSelected.classList.add("selection");
  textSelected.textContent = text.substring(selectionStart, selectionEnd);

  // Render the text after the selection.
  const textAfter = document.createElement("span");
  textAfter.textContent = text.substring(selectionEnd);

  editorEl.appendChild(textBefore);
  editorEl.appendChild(textSelected);
  editorEl.appendChild(textAfter);

  console.log(`Text before selection: ${textBefore.textContent}`);
  console.log(`Selected text: ${textSelected.textContent}`);
  console.log(`Text after selection: ${textAfter.textContent}`);
});

Specifications

Specification
EditContext API
# dom-textupdateevent-selectionstart

Browser compatibility

BCD tables only load in the browser