In which situations should I use 'while loops' instead' for loops' in JavaScript? - Stack Overfl

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I've been always confused at the time to choose between the for and while loop. In which situations should I use 'while loops' instead' for loops' in JavaScript? Does it make a difference?

I've been always confused at the time to choose between the for and while loop. In which situations should I use 'while loops' instead' for loops' in JavaScript? Does it make a difference?

• javascript
• for-loop
• while-loop

Share Improve this question Follow asked Nov 13, 2011 at 4:00 wycwyc 55.4k8383 gold badges256256 silver badges441441 bronze badges

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4 Answers 4

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In terms of "what works", they're interchangeable.

In terms of best practices and conventions, for loops are for a known number of iterations and while loops are to be executed until their intended job is done.

There are three things you might have in a loop control structure: Something you do before the loop (like set the loop variable to zero), something you do in each iteration of the loop (like increment the loop variable), and something you do to tell if you're done looping (like pare the loop variable to something). If you have all three, and they're all simple, use for. If you only have a condition to tell if you're done looping, use while.

(This will soon get closed as too subjective, or moved to another forum, but anyway...)

Obviously any for loop can easily be rewritten using "while". But given the syntax of:

for ([initialization]; [condition]; [final-expression])

that is used by the for loop it is obviously very well suited to situations where there is some simple initialisation and a simple end-of-iteration update or counter increment. Putting all of the loop control logic right there in the loop's opening statement makes it easy to see at a glance what makes the loop tick.

With a while loop the end-of-iteration processing generally has to happen at the bottom of the loop's body, so it's harder to see at a glance how the loop works, but also that is much more suited to the situation where you have to perform a number of calculations to decide whether to keep the loop going.

Of course you can shove multiple statements in a for loop initialisation or final-expression by separating them with mas, but if that is anything more plicated than i++, j++, k-- it quickly gets too messy for my taste and a while loop would be a better choice.

For loops are great for doing the same task over and over when you know ahead of time how many times you'll have to repeat the loop.

On the other hand, while loops are ideal when you have to loop, but you don't know ahead of time how many times you'll need to loop.

Say, for example, you wanted to keep choosing playing cards from a deck until you get a spade. You don't know how many cards you'll need to choose, so a for loop won't work. In situations like these where you don't know in advance when to stop looping, we can use a while loop.

Courtesy: codecademy.

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