Especially when looping, a program often needs to “update” a binding to hold a value based on that binding’s previous value.
counter = counter + 1;
JavaScript provides a shortcut for this.
counter += 1;
Similar shortcuts work for many other operators, such as result *= 2 to double result or counter -= 1 to count downward.
This allows us to shorten our counting example a little more.
for (let number = 0;
number <= 12;
number += 2) {
console.log(number);
}
For counter += 1 and counter -= 1, there are even shorter equivalents: counter++ and counter-.
Source: Haverbeke Marijn (2018), Eloquent JavaScript: A Modern Introduction to Programming,
No Starch Press; 3rd edition.