code: function setProps (props) {
      props = props || {}
  
      //
      if (props.itemsNum === undefined) {
        throw new Error('`opts.itemsNum` must be declared')
      } else {
        this.props.itemsNum = props.itemsNum
      }
  
      this.props.injectBaseCSS = props.injectBaseCSS === undefined
      this.props.startAngle = props.startAngle === undefined ? 90 : props.startAngle
      this.props.endAngle = props.endAngle === undefined ? 0 : props.endAngle
      this.props.radius = props.radius || 80
      this.props.itemAnimationDelay = props.itemAnimationDelay || 0.04
      this.props.animationDuration = props.animationDuration || 0.4
      this.props.fatherElement = props.fatherElement || document.body
      this.props.elements = {}
      this.props.itemWidth = props.itemWidth || 50
      this.props.mainContent = props.mainContent || '+'
      this.props.CSSClassPrefix = props.CSSClassPrefix || 'blooming-menu__'
    }
docs: Private -------