How can Remix Ethereum decode output address of smart contract is created from another smart contract

Question

I have seen that when I create a new smart contract from another smart contract Remix Ethereum return to me the address of smart contract. But When I do it with web3js the callback function just return to me a transactionHash and no more information. When I try to get eth.getTransactionReceipt("transactionHash") I saw contractAddress is null.

I can work arround by use event but my question is that How can Remix Ethereum can do that?

pragma solidity ^0.4.24;

contract Project {
    address public founder;
    constructor () public {
        founder = msg.sender;
    }
    function createRequest(string _title) public returns (address) {
        address addrRequest = new Request(_title);
        return addrRequest;
    }
}

contract Request {
    string public title;
    constructor(string _title) public {
        title = _title;
    }
}

Result from remix ethereum tool

Answer 1

The return value of a sendTransaction method is always the hash of the transaction that’s created. Transactions don’t return a contract value to the front end because transactions are not immediately mined and included in the blockchain. To get values from a function you should use solidity events.

Refer to this blog for understanding more about solidity events.

Refer this question to understand why to write return statements in solidity function.