SingleAxis = function (dim, scale, coordExtent, axisType, position) {

    Axis.call(this, dim, scale, coordExtent);

    /**
     * Axis type
     * - 'category'
     * - 'value'
     * - 'time'
     * - 'log'
     * @type {string}
     */
    this.type = axisType || 'value';

    /**
     * Axis position
     *  - 'top'
     *  - 'bottom'
     *  - 'left'
     *  - 'right'
     *  @type {string}
     */
    this.position = position || 'bottom';

    /**
     * Axis orient
     *  - 'horizontal'
     *  - 'vertical'
     * @type {[type]}
     */
    this.orient = null;

}
Get axis, add it just for draw tooltip.

@return {[type]} [description]