How to set the gas price when I send ERC20 tokens

[web3dapp]

Hi all, one newbie question.
When I send ERC20 token using the "transfer" function, I don't need to handle the stuff like gas price, nonce etc. Are they handled by ethers.js? Is there a way to set the gas price by myself? thank you!

The code like below:

// Connect to the contract
var contractAddress = "0x012345...";
var contractAbiFragment = [
{
"name" : "transfer",
"type" : "function",
"inputs" : [
{
"name" : "_to",
"type" : "address"
},
{
"type" : "uint256",
"name" : "_tokens"
}
],
"constant" : false,
"outputs" : [],
"payable" : false
}
];
var contract = new ethers.Contract(contractAddress, contractAbiFragment, wallet);

// How many tokens?
var numberOfDecimals = 18;
var numberOfTokens = ethers.utils.parseUnits('1.0', numberOfDecimals);

// Send tokens
contract.transfer(targetAddress, numberOfTokens).then(function(tx) {
console.log(tx);
});

[zemse]

When I send ERC20 token using the "transfer" function, I don't need to handle the stuff like gas price, nonce etc. Are they handled by ethers.js?

Yeah, ethers.js tries to populate all the things needed for tx, like gas price, nonce, gas limit. If you want to provide a value for that you can pass an override for it. Docs about overrides are here.

Example code to pass gasPrice override:

const tx = await contract.transfer(targetAddress, numberOfTokens, { gasPrice: ethers.utils.parseUnits('15', 'gwei') })

[web3dapp]

Thanks you zemse! Noted that an override can help. According to Docs, gas price and gas limit can be overridden. Does it support EIP-1559 gas fee also? can I override the priority fee? Thanks

[zemse]

Yep you can also override maxFeePerGas and maxPriorityFeePerGas, it will automatically make it a type 2 tx. You can find the source code about all the overrides here (the docs don't mention it atm, just found that we already have a PR for this).

[web3dapp]

Everything are clear now. Thanks a lot!