这很容易用RegExp实现!

const str = 'Hello RegEx!';
const index = 11;
const replaceWith = 'p';

//'Hello RegEx!'.replace(/^(.{11})(.)/, `$1p`);
str.replace(new RegExp(`^(.{${ index }})(.)`), `$1${ replaceWith }`);

//< "Hello RegExp"

下面是我想出的一个版本，如果你想在react/javascript的索引中设置单词或单个字符的样式。

replaceAt( yourArrayOfIndexes, yourString/orArrayOfStrings ) 

工作示例:https://codesandbox.io/s/ov7zxp9mjq

function replaceAt(indexArray, [...string]) {
    const replaceValue = i => string[i] = <b>{string[i]}</b>;
    indexArray.forEach(replaceValue);
    return string;
}

这是另一种方法

function replaceAt(indexArray, [...string]) {
    const startTag = '<b>';
    const endTag = '</b>';
    const tagLetter = i => string.splice(i, 1, startTag + string[i] + endTag);
    indexArray.forEach(tagLetter);
    return string.join('');
}

和另一个……

function replaceAt(indexArray, [...string]) {
    for (let i = 0; i < indexArray.length; i++) {
        string = Object.assign(string, {
          [indexArray[i]]: <b>{string[indexArray[i]]}</b>
        });
    }
    return string;
}

使用字符串的一行程序。替换回调(不支持表情符号):

// 0 - index to replace, 'f' - replacement string
'dog'.replace(/./g, (c, i) => i == 0? 'f': c)
// "fog"

解释道:

//String.replace will call the callback on each pattern match
//in this case - each character
'dog'.replace(/./g, function (character, index) {
   if (index == 0) //we want to replace the first character
     return 'f'
   return character //leaving other characters the same
})

可以使用以下函数替换字符串特定位置的字符或字符串。使用String.prototype.replaceAllMatches()函数替换以下所有匹配案例。

String.prototype.replaceMatch = function(matchkey, replaceStr, matchIndex) {
    var retStr = this, repeatedIndex = 0;
    for (var x = 0; (matchkey != null) && (retStr.indexOf(matchkey) > -1); x++) {
        if (repeatedIndex == 0 && x == 0) {
            repeatedIndex = retStr.indexOf(matchkey);
        } else { // matchIndex > 0
            repeatedIndex = retStr.indexOf(matchkey, repeatedIndex + 1);
        }
        if (x == matchIndex) {
            retStr = retStr.substring(0, repeatedIndex) + replaceStr + retStr.substring(repeatedIndex + (matchkey.length));
            matchkey = null; // To break the loop.
        }
    }
    return retStr;
};

测试:

var str = "yash yas $dfdas.**";

console.log('Index Matched replace : ', str.replaceMatch('as', '*', 2) );
console.log('Index Matched replace : ', str.replaceMatch('y', '~', 1) );

输出:

Index Matched replace :  yash yas $dfd*.**
Index Matched replace :  yash ~as $dfdas.**

如果你想替换字符串中的字符，你应该创建可变字符串。这些本质上是字符数组。你可以创建一个工厂:

  function MutableString(str) {
    var result = str.split("");
    result.toString = function() {
      return this.join("");
    }
    return result;
  }

然后你可以访问字符，整个数组转换为字符串时使用的字符串:

  var x = MutableString("Hello");
  x[0] = "B"; // yes, we can alter the character
  x.push("!"); // good performance: no new string is created
  var y = "Hi, "+x; // converted to string: "Hi, Bello!"

与vector打交道通常最有效的方法是接触String。

我建议使用以下函数:

String.prototype.replaceAt=function(index, char) {
    var a = this.split("");
    a[index] = char;
    return a.join("");
}

运行这段代码:

String.prototype.replaceAt=function（index， char） { var a = this.split（“”）; a[索引] = 字符; 返回 a.join（“”）; } var str = “hello world”; str = str.replaceAt（3， “#”）; document.write（str）;