FundMe contract - += vs = in fund

[tomasignacioc]

In the line 34 of the FundMe contract, first Patrick writes it like this:

addressToAmountFunded[msg.sender] = msg.value;

But out of nowhere it changes to:

addressToAmountFunded[msg.sender] += msg.value;

I know how the operators works in JavaScript, but here I left the function with only the "=" and it works fine. So what is the difference?

[PatrickAlphaC]

You'll want to do use +=

• = will set the addressToAmountFunded[msg.sender] always equal to whatever msg.value is.
• += will update it

Here is a scenario:

I fund with 1 ETH, then I fund with 2 ETH. addressToAmountFunded[msg.sender] should now be 3 ETH, however:

• The = way will only show 2 ETH
• The += way will show 3 ETH (correctly)

Does that make sense? Do you have the timestamp where it magically changes? Maybe we should add that to ./chronological-updates.md?

[tomasignacioc]

OF COURSE!!! That covers the case when a funder sends eth more than once. The contract finds the funder address and adds up the new donation! Such a rookie mistake from Mr. "I know how the operators works in JavaScript" lol.

The timestamp is 4:34:27

[PatrickAlphaC]

Awesome! And no worries! This was a great question to ask, thank you!