Function extendSelection

static/editor.md/lib/codemirror/lib/codemirror.js:2039–2041

(doc, head, other, options)

  // Extend the primary selection range, discard the rest.
  function extendSelection(doc, head, other, options) {
    setSelection(doc, new Selection([extendRange(doc, doc.sel.primary(), head, other)], 0), options);
  }

  // Extend all selections (pos is an array of selections with length
  // equal the number of selections)