您可以使用Map，并将对象循环两次来完成此作业：

FinalArray=[
{ColumnName:'Name',ID:6,TranslatedText:'Name',Category:'Assigned Employee'},
{ColumnName:'Name',ID:7,TranslatedText:'Name',Category:'Requested Employee'},
{ColumnName:'Designation',ID:8,TranslatedText:'Designation',Category:'Employee'},
{ColumnName:'Occupation',ID:9,TranslatedText:'Occupation',Category:'Assigned Employee'},
{ColumnName:'Occupation',ID:10,TranslatedText:'Occupation',Category:'Requested Employee'}
];

let map = new Map();
FinalArray.forEach((obj)=>
{
  let count = map.get(obj.TranslatedText);
  if (count)
  {
    map.set(obj.TranslatedText, count + 1);
  }
  else
  {
    map.set(obj.TranslatedText, 1);
  }
});
FinalArray.forEach((obj)=>
{
  let count = map.get(obj.TranslatedText);
  if (count > 1)
  {
    obj.TranslatedText = "Rep - " + obj.TranslatedText;
  }

});
console.log(FinalArray);

但是，这会将Rep -添加到所有重复项的前面。如果您只需要连续的重复项，这会很难看，但它是有效的：

FinalArray=[
{ColumnName:'Name',ID:6,TranslatedText:'Name',Category:'Assigned Employee'},
{ColumnName:'Name',ID:7,TranslatedText:'Name',Category:'Requested Employee'},
{ColumnName:'Designation',ID:8,TranslatedText:'Designation',Category:'Employee'},
{ColumnName:'Occupation',ID:9,TranslatedText:'Occupation',Category:'Assigned Employee'},
{ColumnName:'Occupation',ID:10,TranslatedText:'Occupation',Category:'Requested Employee'}
];

let prevObj, foundOne;
FinalArray.push({}); // Removed later via pop(); it causes
                     // one additional iteration so that
                     // the orignial last-object gets processed
FinalArray.forEach((obj)=>
{
  if (prevObj && prevObj.TranslatedText === obj.TranslatedText)
  {
    foundOne = true;
    prevObj.TranslatedText = "Rep - " + prevObj.TranslatedText;
  }
  else
  {
    if (foundOne)
    {
      prevObj.TranslatedText = "Rep - " + prevObj.TranslatedText;
      foundOne = false;
    }
  }
  prevObj = obj;
});
FinalArray.pop();

console.log(FinalArray);

下面是一种不同的方法，它在数组上使用map函数：

let FinalArray=[
{ColumnName:'Name',ID:6,TranslatedText:'Name',Category:'Assigned Employee'},
{ColumnName:'Name',ID:7,TranslatedText:'Name',Category:'Requested Employee'},
{ColumnName:'Designation',ID:8,TranslatedText:'Designation',Category:'Employee'},
{ColumnName:'Occupation',ID:9,TranslatedText:'Occupation',Category:'Assigned Employee'},
{ColumnName:'Occupation',ID:10,TranslatedText:'Occupation',Category:'Requested Employee'}
];

const key = 'ColumnName', prefix = 'Rep - ';

FinalArray.map((column, index, array) => {
        if(index > 0 && array[index-1][key] === column[key]) {
      array[index-1][key] = prefix + column[key];
      array[index][key] = prefix + column[key];
    }

})

console.table(FinalArray);