项目中的大量if-elseif判断优化

记一次项目中对if-else判断的优化, 本人技术比较菜, 不喜勿喷, 如有建议欢迎提出

在项目中有一个需求:

在表单中通过rentUnit下拉框、billingType下拉框、conversionType下拉框的值判断yearTypeShow、conversionTypeShow下拉框是否显示

if (rentUnit === 0 && billingType === 1) {
          this.conversionTypeShow = 1
          this.yearTypeShow = conversionType === 1 ? 1 : 0
        } else if (rentUnit === 0 && billingType === 2) {
          this.conversionTypeShow = 1
          this.yearTypeShow = conversionType === 1 ? 1 : 0
        } else if (rentUnit === 1 && billingType === 1) {
          this.conversionTypeShow = 1
          this.yearTypeShow = conversionType === 1 ? 1 : 0
        } else if (rentUnit === 1 && billingType === 2) {
          this.conversionTypeShow = 1
          this.yearTypeShow = conversionType === 1 ? 1 : 0
        } else if (rentUnit === 2) {
          this.conversionTypeShow = 0
          this.yearTypeShow = billingType === 2 ? 1 : 0
        } else if (rentUnit === 3) {
          this.conversionTypeShow = 0
          this.yearTypeShow = billingType === 2 ? 1 : 0
        } else if (rentUnit === 4 && billingType === 1) {
          this.conversionTypeShow = 1
          this.yearTypeShow = conversionType === 1 ? 1 : 0
        } else if (rentUnit === 4 && billingType === 2) {
          this.conversionTypeShow = 1
          this.yearTypeShow = conversionType === 1 ? 1 : 0
        } else if (rentUnit === 5) {
          this.conversionTypeShow = 0
          this.yearTypeShow = billingType === 2 ? 1 : 0
        } else if (rentUnit === 6 && billingType === 1) {
          this.conversionTypeShow = 0
          this.yearTypeShow = 1
        } else if (rentUnit === 6 && billingType === 2) {
          this.conversionTypeShow = 1
          this.yearTypeShow = conversionType ? conversionType === 1 ? 1 : 0 : 1
        }

优化后  

var obj = {
          0: () => {
            this.conversionTypeShow = true
            this.yearTypeShow = conversionType ? conversionType === 1 : true
          },
          1: () => {
            this.conversionTypeShow = true
            this.yearTypeShow = conversionType ? conversionType === 1 : true
          },
          2: () => {
            this.conversionTypeShow = false
            this.yearTypeShow = billingType === 2
          },
          3: () => {
            this.conversionTypeShow = false
            this.yearTypeShow = billingType === 2
          },
          4: () => {
            this.conversionTypeShow = true
            this.yearTypeShow = conversionType ? conversionType === 1 : true
          },
          5: () => {
            this.conversionTypeShow = false
            this.yearTypeShow = billingType === 2
          },
          6: () => {
            this.conversionTypeShow = !billingType === 1
            this.yearTypeShow = billingType === 1 ? true : conversionType ? conversionType === 1 : true
          }
        }
        obj[rentUnit]()