JS关于 replace 取值、替换第几个匹配项问题小结

let strtest = "0123测试replace456测试replace789测试replace0"
console.log("原字符串：" + strtest)
let outstr = strtest.replace("测试","ceshi")
console.log("输出字符串：" + outstr)
// 原字符串：0123测试replace456测试replace789测试replace0
// 输出字符串：0123ceshireplace456测试replace789测试replace0

let strtest = "0123测试replace456测试replace789测试replace0"
console.log("原字符串：" + strtest)
let outstr = strtest.replace(/测试/, "ceshi")
console.log("输出字符串：" + outstr)
// 原字符串：0123测试replace456测试replace789测试replace0
// 输出字符串：0123ceshireplace456测试replace789测试replace0

let strtest = '0123测试replace456测试replace789测试replace0';
console.log("原字符串：" + strtest)
let arrstr = strtest.split("测试");
let outstr = arrstr.join("ceshi");
console.log("输出字符串：" + outstr)
// 原字符串：0123测试replace456测试replace789测试replace0
// 输出字符串：0123ceshireplace456ceshireplace789ceshireplace0

let strtest = "0123测试replace456测试replace789测试replace0"
console.log("原字符串：" + strtest)
let outstr = strtest.replace(/测试/g, "ceshi")
// 另一种写法：
// let reg = new RegExp("测试", "g")
// let outstr = strtest.replace(reg, "ceshi")
console.log("输出字符串：" + outstr)
// 原字符串：0123测试replace456测试replace789测试replace0
// 输出字符串：0123ceshireplace456ceshireplace789ceshireplace0

let num = 2 // 定义替换第二个匹配项
let strtest = '0123测试replace456测试replace789测试replace0';
console.log("原字符串：" + strtest)
let arrstr = strtest.split("测试");
if(arrstr.length < num)
    return
let arrstr1=[],arrstr2=[]
for(let ii=0;ii<arrstr.length;ii++){
    if(ii < num)
        arrstr1.push(arrstr[ii])
    else
        arrstr2.push(arrstr[ii])
}
let outstr = arrstr1.join("测试")+"ceshi"+arrstr2.join("测试");
console.log("输出字符串：" + outstr)
// 原字符串：0123测试replace456测试replace789测试replace0
// (index):59 输出字符串：0123测试replace456ceshireplace789测试replace0

let strtest = '0123测试replace456测试replace789测试replace0';
console.log("原字符串：" + strtest)
let outstr = strtest.replace(/((?:.*?测试.*?){1}.*?)测试/m, "$1-ceshi-")
// ?: 表示：其后边的 pattern 匹配但不获取。匹配项被标识为 $1，后续会引用
// .*? 表示：.* 除 '/n' 之外的任意个任意字符
// {1} 表示：其前边的 pattern 出现一次
// /pattern/m 表示： m 全局查询
console.log("输出字符串：" + outstr)
// 原字符串：0123测试replace456测试replace789测试replace0
// 输出字符串：0123测试replace456测试replace789-ceshi-replace0

let strtest = '0123<Object>replace456测试replace78</Object>9测试replace0';
let startstr = "<Object>"
let endstr = "</Object>"
if (strtest.indexOf(startstr) > strtest.indexOf(endstr))
    return
console.log("原字符串：" + strtest)
let arr = strtest.split(startstr)
let arr2 = arr[1].split(endstr)
let resultstr = arr2[0]
let outstr = startstr + resultstr + endstr
console.log("输出字符串：" + outstr)
// 原字符串：0123<Object>replace456测试replace78</Object>9测试replace0
// 输出字符串：<Object>replace456测试replace78</Object>
let strtest = '0123<Object>replace456测试replace78</Object>9测试replace0';
let startstr = "<Object>"
let endstr = "</Object>"
if (strtest.indexOf(startstr) > strtest.indexOf(endstr))
    return
console.log("原字符串：" + strtest)
let arr = strtest.split(startstr)
let arr2 = arr[1].split(endstr)
let resultstr = arr2[0]
let outstr = startstr + resultstr + endstr
console.log("输出字符串：" + outstr)
// 原字符串：0123<Object>replace456测试replace78</Object>9测试replace0
// 输出字符串：<Object>replace456测试replace78</Object>

let strtest = '0123<Object>replace456测试replace78</Object>9测试replace0';
console.log("原字符串：" + strtest)
let outstr = strtest.replace(/<Object>(.*?)<\/Object>/m, "-ceshi-") // \ 为转义字符
console.log("输出字符串：" + outstr)
// 原字符串：0123<Object>replace456测试replace78</Object>9测试replace0
// 输出字符串：0123-ceshi-9测试replace0

let strtest = '0123<Object>replace456测试replace78</Object>9测试replace0';
console.log("原字符串：" + strtest)
let outstr = strtest.match(/<Object>(.*?)<\/Object>/m)
console.log("输出字符串：" + outstr)
// 原字符串：0123<Object>replace456测试replace78</Object>9测试replace0
// 输出字符串：<Object>replace456测试replace78</Object>

let strtest = "这是<Object>要提取的内容</Object>，还有<Object>另一个内容</Object>"
console.log("原字符串：" + strtest)
let regex = /<Object>(.*?)<\/Object>/gm
const matches = []
let match
while ((match = regex.exec(strtest)) !== null) {
    matches.push(match[1])
    console.log(match)
}
console.log("输出全部匹配项：", matches)
// 原字符串：这是<Object>要提取的内容</Object>，还有<Object>另一个内容</Object>
// (2) ["<Object>要提取的内容</Object>", "要提取的内容", index: 2, input: "这是<Object>要提取的内容</Object>，还有<Object>另一个内容</Object>", groups: undefined]
// (2) ["<Object>另一个内容</Object>", "另一个内容", index: 28, input: "这是<Object>要提取的内容</Object>，还有<Object>另一个内容</Object>", groups: undefined]
// 输出全部匹配项： (2) ["要提取的内容", "另一个内容"]