@mason-api/javascript-sdk/src/transformations/textareaValue.js

Mason component rendering library

import _ from 'lodash';
import update from 'immutability-helper';

export default () => (node) => {
  if (node.tag === 'textarea') {
    return update(node, {
      p: { $unset: ['defaultValue'] },
      t: { $set: _.get(node.p, 'defaultValue', '') },
    });
  }
  return node;
};