uni-app页面

计算属性

不需要在data中定义

<template>
    <view>
        <view>Original message: "{{ message }}"</view>
        <view>Computed reversed message: "{{ reversedMessage }}"</view>
        <view>a + b = {{testFun}}</view>
    </view>
</template>

<script>
    export default {
        data() {
            return {
                message: 'Hello',
                a:1,
                b:2,
            }
        },
        computed: {
            // 计算属性的 getter
            reversedMessage: function () {
              // `this` 指向 vm 实例
              return this.message.split('').reverse().join('')
              
            },
            testFun: function () {
                return this.a + this.b
            }
          }
    }
</script>

监听属性

需要在data中定义

<template>
    <view>
        <view>fullName: {{ fullName }}</view>
    </view>
</template>

<script>
    export default {
        data() {
            return {
                firstName: 'Foo',
                lastName: 'Bar',
                fullName: 'Foo Bar',
            }
        },
        watch: {
            firstName: function (oldVal, newVal) {
              this.fullName = newVal + ' ' + this.lastName
            },
            lastName: function (oldVal, newVal) {
              this.fullName = this.firstName + ' ' + newVal
            }
        },
    }
</script>

但是使用计算属性会更简洁

<template>
    <view>
        <view>fullName: {{ fullName }}</view>
    </view>
</template>

<script>
    export default {
        data() {
            return {
                firstName: 'Foo',
                lastName: 'Bar',
            }
        },
        computed: {
            fullName: function () {
                return this.firstName + ' ' + this.lastName
            }
        },
    }
</script>