JavaScript中没有replacat函数。你可以使用下面的代码替换任意字符串中指定位置的任意字符:

函数 rep（） { var str = 'Hello World'; str = setCharAt（str，4，'a'）; 警报; } 函数集CharAt（str，index，chr） { if（索引 > str.length-1） 返回 str; 返回 str.substring（0，index） + chr + str.substring（index+1）; } <button onclick=“rep（）;”>click</button>

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;
}

function dothis() { var x = document.getElementById("x").value; var index = document.getElementById("index").value; var text = document.getElementById("text").value; var length = document.getElementById("length").value; var arr = x.split(""); arr.splice(index, length, text); var result = arr.join(""); document.getElementById('output').innerHTML = result; console.log(result); } dothis(); <input id="x" type="text" value="White Dog" placeholder="Enter Text" /> <input id="index" type="number" min="0"value="6" style="width:50px" placeholder="index" /> <input id="length" type="number" min="0"value="1" style="width:50px" placeholder="length" /> <input id="text" type="text" value="F" placeholder="New character" /> <br> <button id="submit" onclick="dothis()">Run</button> <p id="output"></p>

此方法适用于较小长度的字符串，但对于较大的文本可能很慢。

var x = "White Dog";
var arr = x.split(""); // ["W", "h", "i", "t", "e", " ", "D", "o", "g"]
arr.splice(6, 1, 'F');

/* 
  Here 6 is starting index and 1 is no. of array elements to remove and 
  final argument 'F' is the new character to be inserted. 
*/
var result = arr.join(""); // "White Fog"

解决方案不工作的负索引，所以我添加了一个补丁。

String.prototype.replaceAt=function(index, character) {
    if(index>-1) return this.substr(0, index) + character + this.substr(index+character.length);
    else return this.substr(0, this.length+index) + character + this.substr(index+character.length);
    
}

我做了一个类似于你问的函数，它检查字符串中的字符是否在不允许字符数组中如果是它就用"

    var validate = function(value){
        var notAllowed = [";","_",">","<","'","%","$","&","/","|",":","=","*"];
        for(var i=0; i<value.length; i++){
            if(notAllowed.indexOf(value.charAt(i)) > -1){
               value = value.replace(value.charAt(i), "");
               value = validate(value);
            }
       }
      return value;
   }

我用负下标的安全方法

/**
 * @param {string} str 
 * @param {number} index 
 * @param {string} replacement 
 * @returns {string}
 */
static replaceAt (str, index, replacement)
{
    if (index < 0) index = str.length + index
    if (index < 0 || index >= str.length) throw new Error(`Index (${index}) out of bounds "${str}"`)
    return str.substring(0, index) + replacement + str.substring(index + 1)
}

像这样使用它:

replaceAt('my string', -1, 'G') // 'my strinG'
replaceAt('my string', 2, 'yy') // 'myyystring'
replaceAt('my string', 22, 'yy') // Uncaught Error: Index (22) out of bounds "my string"