React array or iterator should have a unique "key" prop? Please take a look at it.

in order to make every three pictures into a set of pictures, the outer package is marked with a DIV tag.
wrote a utility function filterArray to divide the original array into two arrays. Key and item (each item) are not rendered when map is ergodic, but console.log can come out.
system error Each child in an array or iterator should have a unique "key" prop.
for guidance, thank you

import React, {Component} from "react";
import TactiveItem from".. / tactiveitem/views";
import". / index.css";

/ / every three Filter is a group of
let filterArray = (source, count) = > {
let arr = [];
for (let ionomer < len;i+=3) {

   arr.push(source.slice(i,i+3));

}
return arr;
}

class TactiveList extends Component {

constructor (props) {

super(props);

this.state = {
    title: "",
    listData: [
        {
            id:   "1",
            pic:  "p29/201302/28/3d20251a1b60350a93835fbb",
            tag:  "",
            text: "",
            fav:  "8251",
            istag: true
        },
        {
            id:   "2",
            pic:  "p70/1809/e7/4941057a6aae702",
            text: "",
            fav:  "5775"
        },
        {
            id:   "3",
            pic:  "p60/1809/f4/d19e9608d2d1a002",
            text: "",
            fav:  "8355"
        },
        {
            id:   "4",
            pic:  "p48/201302/28/bc44faa497db0dcf93835fbb",
            text: "",
            fav:  "8436"
        },
        {
            id:   "5",
            pic:  "p49/201302/28/f7876853b1e2279d93835fbb",
            text: "",
            fav:  "5568"
        },
        {
            id:   "6",
            pic:  "p5/1411/67/677f3ca100291a23213a9cdb",
            text: "",
            fav:  "8436"
        }
    ],
    filterItems: []
};

}

render () {

let listData = this.state.listData;                 //
this.state.filterItems = filterArray(listData, 3);  //
/*
**item:[
        {"id":"1","pic":"p29/201302/28/3d20251a1b60350a93835fbb","tag":"","text":"","fav":"8251","istag":true},
        {"id":"2","pic":"p70/1809/e7/4941057a6aae702","text":"","fav":"5775"},
        {"id":"3","pic":"p60/1809/f4/d19e9608d2d1a002","text":"","fav":"8355"}
    ]
**item:[
        {"id":"4","pic":"p48/201302/28/bc44faa497db0dcf93835fbb","text":"","fav":"8436"},
        {"id":"5","pic":"p49/201302/28/f7876853b1e2279d93835fbb","text":"","fav":"5568"},
        {"id":"6","pic":"p5/1411/67/677f3ca100291a23213a9cdb","text":"","fav":"8436"}
    ]
**
*/
return (
  <div className="m-dest m-dest-default">
    <h5 className="title">{this.state.title}</h5>
    <div className="list">
        {
            this.state.filterItems.map((item) => {
                //Each child in an array or iterator should have a unique "key" prop.
                return <div><TactiveItem key={item.id} itemData={item} /></div>        
            })

        }
    </div>
  </div>
);

}
}

export default TactiveList;

problem description

the environmental background of the problems and what methods you have tried

related codes

/ / Please paste the code text below (do not replace the code with pictures)

what result do you expect? What is the error message actually seen?

this.state.filterItems.map((item, index) => { //Each child in an array or iterator should have a unique "key" prop. return <div key={index}><TactiveItem itemData={item} /></div> })