10进制转62进制，把大小写字母充当占位符
let tmp = template()
let str = toSixTwo(100004)
let num = toTen(str)
console.log(str) // qRp
console.log(num) // 100004
// 33-47=14 58-64=6 91-96=5 123-126=3 65-90=25 97-122=25
// 10进制转成62进制
function toSixTwo(num) {
let rule = 61
let a = num % rule
let b = (num / rule) >> 0
let str = tmp[a]
let index = 0
while (b>0){
index++
a = b%rule
b = (b / rule) >> 0
str = tmp[a] + str
}
return str
}
// 62转10进制
function toTen(numStr){
let rule = 61
let arr = numStr.split('')
let num = 0
arr.reverse()
arr.map((value,index)=>{
console.log(value)
num += (tmp.findIndex(val=>val===value) * Math.pow(rule,index))
})
return num
}
// 生成模板
function template(){
let arr = []
let lower = 97
let upper = 65
let letterNum = 122-lower+1
for(let i=0;i<62;i++){
if(i<10){
arr.push(i.toString())
}else if(i<10+letterNum){
arr.push(String.fromCharCode(lower))
lower++
}else if(i<10+letterNum+letterNum) {
arr.push(String.fromCharCode(upper))
upper++
}
}
return arr
}
