TRC-20: Token Standard on Tron

pragma solidity ^0.5.8;

contract TRC20Token {
    string public name = "Sample TRC20 Token";
    string public symbol = "ST20";
    uint8 public decimals = 18;
    uint256 public totalSupply = 1000000 * (10 ** uint256(decimals));
    
    mapping (address => uint256) public balanceOf;
    mapping (address => mapping (address => uint256)) public allowance;
    
    event Transfer(address indexed from, address indexed to, uint256 value);
    event Approval(address indexed owner, address indexed spender, uint256 value);
    
    constructor() public {
        balanceOf[msg.sender] = totalSupply;
    }
    
    function transfer(address _to, uint256 _value) public returns (bool success) {
        require(_to != address(0));
        require(balanceOf[msg.sender] >= _value);
        
        balanceOf[msg.sender] -= _value;
        balanceOf[_to] += _value;
        
        emit Transfer(msg.sender, _to, _value);
        return true;
    }
    
    function approve(address _spender, uint256 _value) public returns (bool success) {
        allowance[msg.sender][_spender] = _value;
        emit Approval(msg.sender, _spender, _value);
        return true;
    }
    
    function transferFrom(address _from, address _to, uint256 _value) public returns (bool success) {
        require(_to != address(0));
        require(balanceOf[_from] >= _value);
        require(allowance[_from][msg.sender] >= _value);
        
        balanceOf[_from] -= _value;
        balanceOf[_to] += _value;
        allowance[_from][msg.sender] -= _value;
        
        emit Transfer(_from, _to, _value);
        return true;
    }
}