Function detectViewMode

tests/responsive.property.test.js:50–52

* Helper function to simulate BookUI view mode detection * This mirrors the logic in BookUI.detectViewMode() * @param {number} width - Screen width in pixels * @returns {string} - Detected view mode: 'single' or 'double'

(width)

   * @returns {string} - Detected view mode: 'single' or 'double'
   */
  function detectViewMode(width) {
    return width < BREAKPOINT ? 'single' : 'double';
  }

  /**
   * Property 6.1: 屏幕宽度小于768px时应显示单页视图模式