CODEWITHSUNDEEP
javascript
localhost
localhost

Reputation: 861

Difference between increment of the loop

While reading a blog, i came across a condition, which goes into infinite loop, but i didn't understand why, if we try following code 

for (a=5; a < 10; a+1){
console.log(a);
}

this runs as a infinite loop, but with the following it runs fine

for (a=5; a < 10; a++){
console.log(a);
}

what is the main difference?

Upvotes: 0

Views: 87

Answers (7)

younes rami
younes rami

Reputation: 81

At the first example you are not increment the value of a for (a=5; a < 10; a+1 <--- a+1 is not how to add 1 to a value You can use a++

Upvotes: -3

Nina Scholz
Nina Scholz

Reputation: 386654

The part

for (a = 5; a < 10; a + 1) {
//                  ^^^^^

does not change a

You need an assignment

for (a = 5; a < 10; a = a + 1) {
//                  ^^^

If you use a++ then it resolves to a = a + 1

The operator ++ is an increment operator.

Upvotes: 8

jamil tero
jamil tero

Reputation: 77

a++ means a=a+1 while a+1 doesn't store the value in a which means a will still 5 forever

Upvotes: 0

Mathieu Turcotte
Mathieu Turcotte

Reputation: 354

The problem is the a+1 part. a+1 simply returns the value of a+1. It doesn't affect anything back to a. a++ actually returns a and then increments it.

Upvotes: 1

FalcoB
FalcoB

Reputation: 1333

it is because it says: a is 0; loop through as long as it is smaller ten; then 1 (becaus 0+1)

you need to add a++ or a = a+1

Upvotes: -1

T.J. Crowder
T.J. Crowder

Reputation: 1074475

a++ adds one to a and stores the result in a.¹

a + 1 just adds one to a, without storing the result in a. (E.g., so you can use the resulting value for something else: b = a + 1.)

In the "update" (increment) part of a for, you want to modify the loop variable. So you want a++ (or ++a), not a + 1.

¹ Specifically, a++ (a postfix increment) reads the value of a, adds one to a, and then makes a's previous value the result of the expression. So a = 1; b = a++; leaves us with b == 1 and a == 2.

There's also ++a (a prefix increment), which adds one to a and then uses the resulting value in a as the expression's result. So a = 1; b = ++a; leaves us with b == 2 and a == 2.

This is sort of indicated visually: In a++, the a is first, and the increment comes after, and indeed the resulting value of that is of a before it was incremented. In ++a, the increment comes first, then the a, which also indicates what we get as a result.

Upvotes: 3

Ricardo Pontual
Ricardo Pontual

Reputation: 3757

The first loop is not incrementing the a variable doing a+1, the correct is a=a+1:

for (a=5; a < 10; a=a+1){
console.log(a);
}

Upvotes: 0

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