++value vs value++
Written byPhuoc Nguyen
Created
15 Jul, 2020
Last updated
22 Aug, 2022
Category
JavaScript
Contributors
`++` is the increment operator adding one to the operand.
There're two variables of the operator which use `++` as prefix or postfix: `++value` and `value++`.They have the same effect in for loops. The following loops print the same results which are the numbers from 0 to 4:
js
for (let i = 0; i < 5; i++) {
console.log(i);
}
// And
for (let i = 0; i < 5; ++i) {
console.log(i);
}#Differences
When returning a value,
`return value++` returns the original value before the value is increased. While `return ++value` increases the value and returns the updated value.The following
`foo` and `bar` functions returns different results:js
const foo = (x) => x++;
const bar = (x) => ++x;
foo(1); // 1
bar(1); // 2#Good to know
`value += 1` is another alternative of the postfix increment `value++`. It's worth noting that they can provide different result when using with strings.The postfix increment
`value++` will convert the value to number first, and then increase the value:js
let value = '5';
value++;
value; // 6On the other hand, if value is a string,
`value += 1` converts the second argument (`1`) to string first, and then concatenate them together.js
let value = '5';
value += 1;
value; // '51'
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Phước Nguyễn