js如何在字符串中查找某个字符的位置

const str = "Hello, world!";  
const search = "o";  
const index = str.indexOf(search);  
  
if (index !== -1) {  
  console.log(`The character '${search}' is found at index '${index}'.`);  
} else {  
  console.log(`The character '${search}' is not found in the string.`);  
}

const str = "Hello, world!";  
const search = "o";  
const index = str.indexOf(search);  
  
if (index !== -1) {  
  console.log(`The character '${search}' is found at index '${index}'.`);  
  console.log(str.charAt(index));  
} else {  
  console.log(`The character '${search}' is not found in the string.`);  
}

const str = "Hello, world!";  
const search = "o";  
const newStr = str.replace(search, "x");  
  
console.log(`The character '${search}' is found at index '${index}'.`);  
console.log(newStr);

let a = 'dafdsafasdfadgdafasfsagadfasfsafsadfsda';
let str = 'da';
let b = a.indexOf(str);
let i = 0;
let locationList = [];
let locationObj = {};
 
while(a.indexOf(str,i) !== -1){
locationObj = {};
locationObj.startNum = a.indexOf(str,i);
locationObj.endNum = a.indexOf(str,i) + str.length - 1
locationList.push(locationObj);
console.log("开始",i);
console.log("起始位置",a.indexOf(str,i));
console.log("结束位置",a.indexOf(str,i) + str.length - 1);
console.log("三种情况：1、选择位置在首位，2、选择位置在中间，3、选择位置在末尾");
  i = a.indexOf(str,i) + str.length;
}
let d = a.split(str);
for(let i = d.length - 1;i >=0 ; i--){
    if(i !== 0){
      d.splice(i , 0 ,str);
    }
}
if(d[0] === '') d.splice(0,1);
if(d[d.length - 1] === '') d.splice(d.length - 1,1);
console.log("c===================>", d);
 
let oneList = [];
let oneObj = {
      
    };
for(let i = 0;i<d.length;i++){
    oneObj = {  }
    if(d[i] === str){
        oneObj.text = d[i];
        oneObj.isSelect = true;
        oneObj.isActive = false;
        if(i !== 0) {
            oneObj.startNum = locationList[oneList[i - 1].index].startNum
            oneObj.endNum = locationList[oneList[i - 1].index].endNum
            oneObj.index = oneList[i - 1].index + 1;
        }
        else {
            oneObj.startNum = locationList[0].startNum
            oneObj.endNum = locationList[0].endNum
            oneObj.index = 1
        }
    }else{
        oneObj.text = d[i];
        oneObj.isSelect = false;
        oneObj.isActive = false;
         if(i !== 0) oneObj.index = oneList[i - 1].index;
         else oneObj.index = 0
    }
oneList.push(oneObj);
}
console.log("oneList=================>", oneList);