不要在map调用中添加分号，但在最后的join调用中将其用作分隔符。
不是问题，但是：

• 你可以使用Boolean作为过滤器回调函数。
• 当.checked为false时，您可以返回.checked，而不是返回''，这允许您返回一个没有if..else的表达式。
• 可以使用模板字符串来用逗号连接属性。

const arr = [{"id": "753311","role": "System Of Record (SOR)","license": "Target","DC": "Client · L2 (Inactive), Account · L1","managedGeography": "North America · L2, International · L2","managedSegment": "Institutional Clients Group [L3], Discontinued Ops [L2]","checked": true,"checkBoxPatched": true},{"id": "752872","role": "Authorized Redistributor (AR)","license": "Interim","DC": "Holding · L1, Document · L1, Compliance · L1","managedGeography": "Unspecified","managedSegment": "Unspecified","checked": true,"checkBoxPatched": true},{"id": "752583","role": "Authorized Redistributor (AR)","license": "Target","DC": "Agreement · L1, Asset · L1, Activity · L1, Account · L1","managedGeography": "Unspecified", "managedSegment": "Unspecified"}];

let adsList = arr.map(obj =>
    obj.checked && `${obj.role}, ${obj.license}, ${obj.DC}, ${obj.managedGeography}, ${obj.managedSegment}`
).filter(Boolean).join(';\n\n');
      
 console.log(adsList)

您可以更新代码以使用;\n连接数组，如果您希望保留中间的额外行，则使用;\n\n

let adsList = arr.map(selectedObj => {
    if (selectedObj.checked) {
        return selectedObj.role + ", " + selectedObj.license + ", " + selectedObj.DC + ", " + selectedObj.managedGeography + ", " + selectedObj.managedSegment;
    } else {
        return '';
    }
}).filter((str) => str.length > 0).join(';\n');

const arr = [{
    "id": "753311",
    "role": "System Of Record (SOR)",
    "license": "Target",
    "DC": "Client · L2 (Inactive), Account · L1",
    "managedGeography": "North America · L2, International · L2",
    "managedSegment": "Institutional Clients Group [L3], Discontinued Ops [L2]",
    "checked": true,
    "checkBoxPatched": true
  },
  {
    "id": "752872",
    "role": "Authorized Redistributor (AR)",
    "license": "Interim",
    "DC": "Holding · L1, Document · L1, Compliance · L1",
    "managedGeography": "Unspecified",
    "managedSegment": "Unspecified",
    "checked": true,
    "checkBoxPatched": true
  },
  {
    "id": "752583",
    "role": "Authorized Redistributor (AR)",
    "license": "Target",
    "DC": "Agreement · L1, Asset · L1, Activity · L1, Account · L1",
    "managedGeography": "Unspecified",
    "managedSegment": "Unspecified"
  }
]

let adsList = arr.map(selectedObj => {
  if (selectedObj.checked) {
    return selectedObj.role + ", " + selectedObj.license + ", " + selectedObj.DC + ", " + selectedObj.managedGeography + ", " + selectedObj.managedSegment;
  } else {
    return '';
  }
}).filter((str) => str.length > 0).join(';\n\n');

console.log(adsList)

可以使用slice()方法从结果字符串中删除最后一个字符：

let adsList = arr.map(selectedObj => {
  if (selectedObj.checked) {
    return selectedObj.role + ", " + selectedObj.license + ", " + selectedObj.DC + ", " + selectedObj.managedGeography + ", " + selectedObj.managedSegment + ";\n"
  } 
  return '';
}).filter((str) => str.length !== 0).join('\n').slice(0, -2);

console.log(adsList)

可以使用以下正则表达式：

/;(\s|\\n)*$/

若要在字符串末尾找到分号，然后将其替换为空字符串。
正则表达式具有以下含义：
;匹配文字分号
(\s|\\n)*匹配一个或多白色或\n文字
$匹配字符串的结尾

const arr = [
    {
        "id": "753311",
        "role": "System Of Record (SOR)",
        "license": "Target",
        "DC": "Client · L2 (Inactive), Account · L1",
        "managedGeography": "North America · L2, International · L2",
        "managedSegment": "Institutional Clients Group [L3], Discontinued Ops [L2]",
        "checked": true,
        "checkBoxPatched": true
    },
    {
        "id": "752872",
        "role": "Authorized Redistributor (AR)",
        "license": "Interim",
        "DC": "Holding · L1, Document · L1, Compliance · L1",
        "managedGeography": "Unspecified",
        "managedSegment": "Unspecified",
        "checked": true,
        "checkBoxPatched": true
    },
    {
        "id": "752583",
        "role": "Authorized Redistributor (AR)",
        "license": "Target",
        "DC": "Agreement · L1, Asset · L1, Activity · L1, Account · L1",
        "managedGeography": "Unspecified",
        "managedSegment": "Unspecified"
    }
]

let adsList = arr.map(selectedObj => {
        if (selectedObj.checked) {
          return selectedObj.role + ", " + selectedObj.license + ", " + selectedObj.DC + ", " + selectedObj.managedGeography + ", " + selectedObj.managedSegment + ";\n"
        } else {
          return '';
        }
      }).filter((str) => str.length !== 0).join('\n').replace(/;(\s|\\n)*$/, '');
      
 console.log(adsList)