JavaScript中字符串相关的方法使用总结

const str="Hello,世界!";
console.log(str.charAt(0)); //H
console.log(str.charAt(7)); //界
console.log(str.charCodeAt(0)); //72
console.log(str.charCodeAt(7)); //30028
console.log(parseInt(30028).toString(16)); //754c

const str = "ab😂ba";
console.log(str.charCodeAt(2)); // 55357
console.log(str.codePointAt(2)); // 128514

// 使用 fromCharCode() 创建字符
const char1 = String.fromCharCode(65); // 65 是字符 'A' 的UTF-16码元
console.log(char1); // 输出：A
// 使用 fromCodePoint() 创建字符
const char2 = String.fromCodePoint(128514); // 128514 是笑脸符号的码点
console.log(char2); // 输出：😂

const char1 = 'A';   // 拉丁字母大写A
const char2 = 'Α';  // 希腊字母大写Alpha
// 比较两个字符是否相等
console.log(char1 === char2); // 输出：false，尽管外观相似，但字符编码不同
// 获取字符编码
console.log(char1.charCodeAt(0)); // 输出：65，字符A的Unicode编码
console.log(char2.charCodeAt(0)); // 输出：913，字符Α的Unicode编码

let str="Hello "
console.log(str.concat("World","!")) //"Hello World!"
console.log(str) //"Hello"

let str = "Hello world!"
console.log(str.slice(0)) //Hello world!
console.log(str.slice(0, 5)) //Hello
console.log(str.substring(0)) //Hello world!
console.log(str.substring(0, 5)) //Hello
console.log(str.substr(0)) //Hello world!
console.log(str.substr(0, 5)) //Hello
console.log(str.slice(-5)) //orld!
console.log(str.substring(-5)) //Hello world!
console.log(str.substr(-5)) //orld!
console.log(str.slice(0, -5)) //Hello w
console.log(str.substring(0, -5)) //空字符串
console.log(str.substr(0, -5)) //空字符串
console.log(str.slice(-5, -2)) //orl
console.log(str.substring(-5, -2)) //空字符串
console.log(str.substr(-5, -2)) //空字符串
console.log(str.slice(-2, -5)) //空字符串
console.log(str.substring(-2, -5)) //空字符串
console.log(str.substr(-2, -5)) //空字符串
console.log(str.slice(5, 0)) //空字符串
console.log(str.substring(5, 0)) //Hello
console.log(str.substr(5, 0)) //空字符串

let str = "Hello"
console.log(str.padStart(10, "World")) //WorldHello
console.log(str.padEnd(10, "World")) //HelloWorld

let str = "To be what we are, and to become what we are capable of becoming, is the only end of life."
// 使用match匹配所有包含a的单词
let reg1 = /\b[a-zA-Z]*a[a-zA-Z]*\b/g
console.log(str.match(reg1)) // [ 'what', 'are', 'and', 'what', 'are', 'capable' ]
// 使用match匹配包含a的单词，不使用全局匹配
let reg2 = /\b[a-zA-Z]*a[a-zA-Z]*\b/
console.log(str.match(reg2))
// [
//   'what',
//   index: 6,
//   input: 'To be what we are, and to become what we are capable of becoming, is the only end of life.',
//   groups: undefined
// ]

let str = "To be what we are, and to become what we are capable of becoming, is the only end of life."
// 使用search匹配we
let reg = /we/g
console.log(str.search(reg)) // 11

const originalString = "Hello, world! Hello, universe!";
// 替换字符串中的单个匹配项
const replacedString1 = originalString.replace("world", "friends");
console.log(replacedString1); // 输出：Hello, friends! Hello, universe!
// 使用正则表达式进行替换（只替换第一个匹配项）
const replacedString2 = originalString.replace(/Hello/, "Hi");
console.log(replacedString2); // 输出：Hi, world! Hello, universe!
// 使用正则表达式进行替换（替换所有匹配项）
const replacedString3 = originalString.replace(/Hello/g, "Hi");
console.log(replacedString3); // 输出：Hi, world! Hi, universe!
// 使用$1、$2、$3、$4等来替换匹配项
const replacedString4 = originalString.replace(/(Hello), (world)! (Hello), (universe)!/g, "$3, $4! $1, $2!");
console.log(replacedString4); // 输出：Hello, universe! Hello, world!
// 使用函数来替换匹配项
const replacedString5 = originalString.replace(/(Hello), (world)! (Hello), (universe)!/g, 
function (matched, p1, p2, p3, p4, offset, original) {
    console.log(matched) // 匹配到的字符串
    console.log(offset) // 匹配到的字符串在原字符串中的偏移量
    console.log(original) // 原字符串
    return p3 + ", " + p4 + "! " + p1 + ", " + p2 + "!";
}
);
console.log(replacedString5); // 输出：Hello, universe! Hello, world!

const str="apple,banana,orange"
//以逗号作为分隔符
console.log(str.split(",")) //["apple","banana","orange"]
//限定数组大小
console.log(str.split(",",2)) //["apple","banana"]
//使用正则表达式
const text="apple   orange\tbanana"
const parts=text.split(/\s+/) //匹配连续空格
console.log(parts) //["apple","orange","banana"]

const str = "abc"
const str2 = str[Symbol.iterator]()
console.log(str2.next()) //{ value: 'a', done: false }
console.log(str2.next()) //{ value: 'b', done: false }
console.log(str2.next()) //{ value: 'c', done: false }
console.log(str2.next()) //{ value: undefined, done: true }