JavaScript only run operation if the operation result is < 100

How can I run in JavaScript a operation, ONLY if the operation result is < 100, as an example.

I tried the following code but the += operation got executed twice, but I only want it to be executed after the if statement.

let progress = 0

function earn(howmuch) {
    if (progress += howmuch < 100) {
        console.log(progress) // console.logs 1
        progress += howmuch
        console.log(progress) // console.logs 2
    }
}

document.querySelector('.click-area').addEventListener('click', function() {
    earn(1)
}

Thanks for help