对应关系： 1 - A， 26 - Z， 27 - AA
实现效果：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<div>
<p>第一种方法实现:</p>
输入大于0的整数：<input type="number" class="num" />
<button onclick="change()">转换</button>
转换后的字母：<span id="resString"></span>
<p>第二种方法实现:</p>
输入大于0的整数：<input type="number" class="num2" />
<button onclick="change2()">转换</button>
转换后的字母：<span id="resString2"></span>
<p>字母转数字：</p>
输入大写字母：<input type="text" id="txt" onblur="handleBlur()">
转换后的数字: <span id="numString"></span>
</div>
<script>
const handleBlur = () => {
const val = document.getElementById('txt').value
let num = 0
const getLetterNum = (letter) => {
return letter.charCodeAt() - 64 // 大写减64，小写减96
}
for (let i = 0, len = val.length; i < len; i++) {
var letterNum = getLetterNum(val[i])
num += letterNum * Math.pow(26, len - 1 - i)
}
document.getElementById('numString').innerText = num
}
const change2 = () => {
const strArray = []
const numToString = (nnum) => {
const num = nnum - 1
const integer = parseInt(num / 26)
const remainder = num % 26
const str = String.fromCharCode(64 + parseInt(remainder + 1))
strArray.push(str)
if (integer > 0) {
numToString(integer)
}
}
const value = document.getElementsByClassName('num2')[0].value
numToString(value)
document.getElementById('resString2').innerText = strArray.reverse().join('')
}
// 实现数字转字母
const change = () => {
// 先获取输入的数字
let num = document.getElementsByClassName('num')[0].value
let str = ''
if (parseInt(num) > 0) {
if (num <= 26) {
str = String.fromCharCode(64 + parseInt(num))
} else {
while (num > 26) {
let count = parseInt(num / 26)
let remainder = num % 26
if (remainder === 0) {
remainder = 26
count--
}
str = String.fromCharCode(64 + parseInt(remainder)) + str
num = count
}
str = String.fromCharCode(64 + num) + str
}
}
document.getElementById('resString').innerText = str
}
</script>
</body>
