iterMap

// SPDX-License-Identifier: GPL-3.0
pragma solidity >=0.6.0 <0.9.0;

struct KeyStruct {
    string key;
    bool deleted;
}

struct ValueStruct {
    string value;
    bool isValue;
    uint index; //删除的时候会用到
}

contract IteratorMap{
    mapping(string => ValueStruct) dataMap;
    KeyStruct[] keyArr;
    constructor(){

    }

    function insert(string memory k,string memory v) external returns (bool){
        if (dataMap[k].isValue){
            return false;
        }
        uint i = keyArr.length;
        dataMap[k] = ValueStruct({value:v,isValue:true,index:i});
        keyArr.push();
        keyArr[i] = KeyStruct({key:k,deleted:false});
        return true;
    }

    function del(string memory k) external {
        require(dataMap[k].isValue);
        delete keyArr[dataMap[k].index]; 
        delete dataMap[k];
    }

    function display() external view returns(string[] memory){
        string[] memory data;
        data = new string[](keyArr.length);
        uint j = 0;
        for (uint i=0;i<keyArr.length;i++){
            if (dataMap[keyArr[i].key].isValue) {
                data[j] = dataMap[keyArr[i].key].value;
                j++;
            }
        }
        return data;
    }
}

const { expect } = require("chai");
const { ethers } = require("hardhat");


describe("contract", function () {
  it("test", async function () {
    const MyContract = await ethers.getContractFactory("IteratorMap");
    const myContract = await MyContract.deploy();
    await myContract.deployed();
    await myContract.insert("6","6");
    await myContract.insert("60","60");
    await myContract.insert("600","600");
    result = await myContract.display();
    console.log("result:",result)
    await myContract.del("60");
    result = await myContract.display();
    console.log("result:",result)
  });
});

  contract
result: [ '6', '60', '600' ]
result: [ '6', '600', '' ]