Reading storage layout in the EVM via web3.js

Read.js

const Web3 = require("web3");
var web3   = new Web3("https://ropsten.infura.io/v3/YOUR-API-KEY"); // use a websocket connection

var contractAddress = "Contract Address"; // 

getStorageValues();

async function getStorageValues(){
    
    // #1 single variable uint
    web3.eth.getStorageAt(contractAddress, 0).then(function(res){
        console.log("firstVar:");
        console.log(res);
        console.log(parseInt(res, 16));
        console.log("----------------------")
        console.log("----------------------")
    });

    // # 2 single variable string
    web3.eth.getStorageAt(contractAddress, 1).then(function(res){
        console.log("secondVar:");
        console.log(res);
        console.log(web3.utils.toAscii(res));
        console.log("----------------------")
        console.log("----------------------")
    });
    
    // #3 a constant
    // Constants are stored in the contract code

    // #4 two variables in one slot
    web3.eth.getStorageAt(contractAddress, 2).then(function(res){
        console.log("thirdVar and fourth var:");
        console.log(res);
        console.log("----------------------")
        console.log("----------------------")
    });


    // #5 staitc array
    web3.eth.getStorageAt(contractAddress, 3).then(function(res){
        console.log("Index 3: numberArray:");
        console.log(res);
        console.log("----------------------")
        console.log("----------------------")
    });

    web3.eth.getStorageAt(contractAddress, 4).then(function(res){
        console.log("Index 4: numberArray");
        console.log(res);
        console.log("----------------------")
        console.log("----------------------")
    });

    web3.eth.getStorageAt(contractAddress, 5).then(function(res){
        console.log("Index 5 numberArray:");
        console.log(res);
        console.log("----------------------")
        console.log("----------------------")
    });
    

    // #6 dynamic array
    resDynamicArray = await web3.eth.getStorageAt(contractAddress, 6);
    console.log("Index: 6 dynamic Array");
    console.log(resDynamicArray);
    newIndex = web3.utils.soliditySha3(6); // Use soliditySha3 instead of SHA3 because they are different
    console.log("new index: " + newIndex);

    // Showing the first value of the dynamic array
    storage01 = await web3.eth.getStorageAt(contractAddress, newIndex);
    console.log("Storage01: " + storage01);

    // Showing the second value of the dynamic array
    console.log(newIndex);
    newIndexPlus1 = BigInt(newIndex) + 1n;  // Increasing the index by one

    var hexIndexPlusOne = BigInt(newIndexPlus1).toString(16); // converting BigInt back to hex
    if (hexIndexPlusOne.length % 2) { // get the padding right
      hexIndexPlusOne = '0' + hexIndexPlusOne;
    }

    hexIndexPlusOne = '0x' + hexIndexPlusOne; // add the hex prefix
    console.log(hexIndexPlusOne)
    storage02 = await web3.eth.getStorageAt(contractAddress, hexIndexPlusOne); // look up the storage slot
    console.log("Storage02: " + storage02);


    // #7 Struct: Each member of a struct has its own continous index
    web3.eth.getStorageAt(contractAddress, 7).then(function(res){
        console.log("Index 7 Struct" + res);
        console.log(web3.utils.toAscii(res));
        console.log("----------------------")
        console.log("----------------------")
    });

    web3.eth.getStorageAt(contractAddress, 8).then(function(res){
        console.log(res);
        console.log("Index 8 Struct" + parseInt(res, 16));
        console.log("----------------------")
        console.log("----------------------")
    });


    #8 Mapping
    In order to read a mapping, you need the index and the key of the element
    newKey = web3.utils.soliditySha3(10, 9); // Use soliditySha3 instead of SHA3 because they are different / key . index
    console.log("Mapping: Key 10");
    web3.eth.getStorageAt(contractAddress, newKey).then(function(res){
        console.log(res);
        console.log(parseInt(res, 16));
        console.log("----------------------")
        console.log("----------------------")
    });
    
    newKey =web3.utils.soliditySha3(11, 9); // Use soliditySha3 instead of SHA3 because they are different / key . index
    console.log("Mapping: Key 11");
    web3.eth.getStorageAt(contractAddress, newKey).then(function(res){
            console.log(res);
            console.log(parseInt(res, 16));
            console.log("----------------------")
            console.log("----------------------")
        });

    }

StorageContract.sol

pragma solidity 0.8.13;

contract StorageContract{
    
    // # 1 single variable uint
    uint256 firstVar = 100;

    // # 2 single variable string
    string secondVar = "Hello World";
    
    // #3 a constant
    string constant myConst = "I am a constant";
    
    // #4 two variables in one slot
    uint128 thirdVar = 5555;
    uint32 fourthVar   = 1000000;
    
    // #5 array
    uint32[20] numberArray = [10,15,20,30,40,50,60,70,100,200,300,400,500,600,700,800,900,1000,2000,3000];
    
    // #6 dynamic size array
    uint256[] dynamicArray;
    
    // #7 Struct
    PersonStruct myPerson;
    
    struct PersonStruct{
        string name;
        uint256 age;
    }
    
    // #8 mapping
    mapping(uint256 => uint256) myMapping;
    

    constructor(){
        myMapping[10] = 12345;
        myMapping[11] = 1234567890;
        
        myPerson.name = "Alice";
        myPerson.age  = 25;
        
        dynamicArray.push(1234);
        dynamicArray.push(5678);
    }   
}