<view class='row item-center'>
　　<button class="buy-num-btn btn-minus" disabled="{{minusStatus}}" plain='ture' bindtap='minusNum'>-</button>
　　<input class='buy-num-txt' type='number' value='{{courseCount}}'></input>
　　<button class="buy-num-btn btn-add" plain='ture' bindtap='addNum'>+</button>
</view>

Page({

  /**
   * 页面的初始数据
   */
  data: {
    minusStatus: true,
    courseCount: 1,   
  },
  //数字加1
  addNum: function() {
    var courseCount = this.data.courseCount;
    courseCount++;
    this.setData({
      courseCount: courseCount,
      minusStatus: false
    })
  },
  //数字减1
  minusNum: function() {
    var courseCount = this.data.courseCount;
    if (courseCount > 1) {
      courseCount--;
    }
    //数字<=1时，开启 - 按钮的disable状态
    var minusStatus = courseCount <= 1 ? true : false; 
    this.setData({
      courseCount: courseCount,
      minusStatus: minusStatus
    });
  }
})