wxs判断wxml中input组件传来的值是否为空应该怎么写呢？感谢大神指点！！！

//wxml

<input bindblur="getSearchContent" placeholder="{{searcharea}}" focus="{{autofocus}}" ></input>

<button bindtap='saveData'>搜索</button>

//wxs

console.log(this.data.save_data)

if (this.data.save_data == '') {

wx.showModal({

title: '提示',

content: '输入不能为空',

success: function(res) {

if (res.confirm) {

console.log('用户点击确定')

}

}

})

}

saveExprs(this.data.save_data)

//获取缓存数据

var exprs = wx.getStorageSync("save_array") || []

this.setData({

arry_data: exprs

})

}