Break statement in javascript array map method [duplicate]

Question

Possible Duplicate:
How to short circuit Array.forEach like calling break?

Is there a way so that I can break out of array map method after my condition is met ? I tried the following which throws "Illegal Break Statement" Error. This is some random example I came up with.

var myArray = [22,34,5,67,99,0];

var hasValueLessThanTen = false;

myArray.map(function (value){
    if(value<10){
      hasValueLessThanTen = true;
      break;
    }
  }
);

We can do using for loops, but I wanted to know whether we can accomplish the same using map method ?

It is in essence a duplicate of the question that Rob W refers to. However, the source of this misunderstanding is the wrong usage of map method, which is intended to, hmmm, map values, so it's not supposed to stop the iteration — Yoni
– Yoni, Commented Sep 4, 2012 at 9:36
@Yoni is correct. If the OP is looking for a breakable forEach loop, consider uing methods such as [].every (return true to continue, non-true to break) or [].some - return true to break, non-true to continue. — Rob W
– Rob W, Commented Sep 4, 2012 at 9:40
alternatively [].reduce. Passing [] as a second argument, and only modifying when conditions are met. — Sandy Gifford
– Sandy Gifford, Commented Aug 1, 2017 at 16:03
Also I don't understand why this was marked as a duplicate. The linked question is about forEach which has a much different solution. — Sandy Gifford
– Sandy Gifford, Commented Aug 1, 2017 at 16:06

João Silva · Accepted Answer · 2012-09-04 13:20:29Z

289

That's not possible using the built-in Array.prototype.map. However, you could use a simple for-loop instead, if you do not intend to map any values:

var hasValueLessThanTen = false;
for (var i = 0; i < myArray.length; i++) {
  if (myArray[i] < 10) {
    hasValueLessThanTen = true;
    break;
  }
}

Or, as suggested by @RobW, use Array.prototype.some to test if there exists at least one element that is less than 10. It will stop looping when some element that matches your function is found:

var hasValueLessThanTen = myArray.some(function (val) { 
  return val < 10;
});

edited Sep 4, 2012 at 13:20

answered Sep 4, 2012 at 9:32

João Silva

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5 Comments

TheOneWhoPrograms Over a year ago

I appreciated the .some example even though Rob had already mentioned it. People don't always look in the comments, but typically atleast scan the code samples!

Vadorequest Over a year ago

Why isn't it possible with the Array.prototype.map ?

Mudassir Ali Over a year ago

@Vadorequest I did post the question when I was js newbie, Array.prototype.map was not supposed to be used that way at all, it is a helper method for a whole different usecase where you want to transform every element of a given array into a different variant. So, when it's going to be about "every element", you would never need a "break" statement, if you need a break statement it means maybe you don't need a map. I posted this question because I was trying to use that as a iterator, if you need iterator then go for the simple for loop or forEach in conjunction with return

cellepo Over a year ago

Appears that for is faster than some: jsperf.com/array-some-vs-loop

Sampath Over a year ago

@MudassirAli I hope you can accept this answer no?

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