JavaScript Increment ++ and Decrement --
A quick lesson in why location of Increment and Decrement matters
Welcome to this weeks JavaScript Quickie — 3 Minute JavaScript Lessons
Increment & Decrement
The increment and decrement operators in JavaScript will add one (+1) or subtract one (-1), respectively, to their operand, and then return a value.
The term operand is used extensively in this article. An operand is the quantity on which an operation is to be done. For example in the math equation 1 + 2, both 1 and 2 are operands, while + is the operator.
Syntax
Consider x to be the operand:
- Increment —
x++or++x - Decrement —
x--or--x
As you can see, the ++/ —- operators can be used before or after the operand. Here’s what that might look in your code:
// Incrementlet a = 1;
a++;
++a;// Decrement
let b = 1;
b--;
--b;
Using ++/-- After the Operand
When you use the increment/decrement operator after the operand, the value will be returned before the operand is increased/decreased.
Check out this example:
// Incrementlet a = 1;console.log(a++); // 1
console.log(a); // 2// Decrementlet b = 1;console.log(b--); // 1
console.log(b); // 0
When we first log out the value of a, or b, neither has changed. That’s because the original value of the operand is being returned prior to the operand being changed. The next time the operator is used, we get the result of the +1, or -1.
Using ++/-- Before the Operand
If you’d rather make the variable increment/decrement before returning, you simply have to use the increment/decrement operator before the operand:
// Incrementlet a = 1;console.log(++a); // 2
console.log(a); // 2// Decrementlet b = 1;console.log(--b); // 0
console.log(b); // 0
As you can see in the above example, but using ++ or -- prior to our variable, the operation executes and adds/subtracts 1 prior to returning. This allows us to instantly log out and see the resulting value.
Closing Notes:
Thanks for reading, and hopefully this was helpful! If you’re ready to finally learn Web Development, check out The Ultimate Guide to Learning Full Stack Web Development in 6 months.
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