grapesjs/src/commands/view/Preview.js

import { each } from 'underscore';

export default {
  getPanels(editor) {
    if (!this.panels) {
      this.panels = editor.Panels.getPanelsEl();
    }

    return this.panels;
  },

  tglPointers(editor, val) {
    const body = editor.Canvas.getBody();
    const elP = body.querySelectorAll(`.${this.ppfx}no-pointer`);
    each(elP, item => (item.style.pointerEvents = val ? '' : 'all'));
  },

  run(editor, sender) {
    this.sender = sender;
    editor.stopCommand('sw-visibility');
    editor.getModel().stopDefault();
    const panels = this.getPanels(editor);
    const canvas = editor.Canvas.getElement();
    const editorEl = editor.getEl();
    const pfx = editor.Config.stylePrefix;

    if (!this.helper) {
      const helper = document.createElement('span');
      helper.className = `${pfx}off-prv fa fa-eye-slash`;
      editorEl.appendChild(helper);
      helper.onclick = () => this.stopCommand();
      this.helper = helper;
    }

    this.helper.style.display = 'inline-block';
    this.tglPointers(editor);
    panels.style.display = 'none';
    const canvasS = canvas.style;
    canvasS.width = '100%';
    canvasS.height = '100%';
    canvasS.top = '0';
    canvasS.left = '0';
    canvasS.padding = '0';
    canvasS.margin = '0';
    editor.refresh();
  },

  stop(editor) {
    const { sender = {} } = this;
    sender.set && sender.set('active', 0);
    const panels = this.getPanels(editor);
    editor.runCommand('sw-visibility');
    editor.getModel().runDefault();
    panels.style.display = '';
    const canvas = editor.Canvas.getElement();
    canvas.setAttribute('style', '');

    if (this.helper) {
      this.helper.style.display = 'none';
    }

    editor.refresh();
    this.tglPointers(editor, 1);
  }
};