经典算法题：输入一个字符串，切换其中字母的大小写，下面将分别使用 正则匹配 和 ASCII编码 判断的形式去实现。
#一、问题示例
示例 1：
- 输入：
A23#$5bcF - 输出：
a23#$5BCf
示例 2：
- 输入：
你好啊%……&001 - 输出：
你好啊%……&001
#二、代码演示
- 正则匹配
// 切换字母大小写 正则
export function switchLetterCase1(s: string): string {
let res = ''
const len = s.length
if (len ===0) return res
const reg1 = /[a-z]/
const reg2 = /[A-Z]/
for (let i = 0; i < len; i++) {
const c = s[i]
if (reg1.test(c)) {
res += c.toUpperCase()
} else if (reg2.test(c)) {
res += c.toLowerCase()
} else {
res += c
}
}
return res
}
- ASCII编码
// 切换字母大小写 ASCII编码
export function switchLetterCase2(s: string): string {
let res = ''
const len = s.length
if (len === 0) return res
for (let i = 0; i < len; i++) {
const c = s[i]
const code = c.charCodeAt(0)
if (code >= 65 && code <= 90) {
res += c.toLowerCase()
} else if (code >= 97 && code <= 122) {
res += c.toUpperCase()
} else {
res += c
}
}
return res
}
#三、单元测试
// 切换字母大小写
import { switchLetterCase1, switchLetterCase2 } from '../switch-letter-case.ts'
describe('切换字母大小写 正则匹配', () => {
it('正常情况', () => {
const s = '12A54btr34Agh89'
const res = switchLetterCase1(s)
expect(res).toBe('12a54BTR34aGH89')
})
it('空字符串', () => {
const res = switchLetterCase1('')
expect(res).toBe('')
})
it('非字母', () => {
const res = switchLetterCase1('你好啊%……&001')
expect(res).toBe('你好啊%……&001')
})
})
describe('切换字母大小写 charCode编码', () => {
it('正常情况', () => {
const s = '12A54btr34Agh89'
const res = switchLetterCase2(s)
expect(res).toBe('12a54BTR34aGH89')
})
it('空字符串', () => {
const res = switchLetterCase2('')
expect(res).toBe('')
})
it('非字母', () => {
const res = switchLetterCase2('你好啊%……&001')
expect(res).toBe('你好啊%……&001')
})
})
#四、性能测试
const s = '12A54$%^&9*btr34Agh8912A54$%^&9*btr34Agh8912A54$%^&9*btr34Agh8912A54$%^&9*btr34Agh89'
console.time('switchLetterCase1')
for (let i = 0; i < 10 * 10000; i++) {
switchLetterCase1(s)
}
console.timeEnd('switchLetterCase1')
console.time('switchLetterCase2')
for (let i = 0; i < 10 * 10000; i++) {
switchLetterCase2(s)
}
console.timeEnd('switchLetterCase2')
function switchLetterCase1(s) { let res = ''
const len = s.length
if (len ===0) return res
const reg1 = /[a-z]/
const reg2 = /[A-Z]/
for (let i = 0; i < len; i++) {
const c = s[i]
if (reg1.test(c)) {
res += c.toUpperCase()
} else if (reg2.test(c)) {
res += c.toLowerCase()
} else {
res += c
}
}
return res
}
// 切换字母大小写 ASCII编码 function switchLetterCase2(s) { let res = ''
const len = s.length
if (len === 0) return res
for (let i = 0; i < len; i++) {
const c = s[i]
const code = c.charCodeAt(0)
if (code >= 65 && code <= 90) {
res += c.toLowerCase()
} else if (code >= 97 && code <= 122) {
res += c.toUpperCase()
} else {
res += c
}
}
return res
}
function run() { const s = '12A54$%^&9btr34Agh8912A54$%^&9btr34Agh8912A54$%^&9btr34Agh8912A54$%^&9btr34Agh89'
let s1 = performance.now()
for (let i = 0; i < 10 * 10000; i++) {
switchLetterCase1(s)
}
document.querySelector('.box1-ms').innerText = performance.now() - s1 + ' ms'
let s2 = performance.now()
for (let i = 0; i < 10 * 10000; i++) {
switchLetterCase2(s)
}
document.querySelector('.box2-ms').innerText = performance.now() - s2 + ' ms'
}
- 使用正则表达式，性能较差
- 使用ASCII码判断，性能较好（推荐）
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