if (this.touchStatus) {
let flag = true
if (!flag) return
flag = false
setTimeout(() => { // 函数节流提升性能
// const startY = this.$refs['A'][0].offsetTop
const touchY = e.touches[0].clientY - 79
const index = Math.floor((touchY - this.startY) / 20)
if (index >= 0 && index < this.latters.length) {
this.$emit('change', this.latters[index])
}
flag = true
}, 16)
}