If I have a function like _.transform.

Somewhere within the iteratee function I encounter an error; how do I exit from the _.transform function?

i.e.

{
  try {
    fs.readFileSync('dog_pics');
  } catch(e) {
    return;
  }
}

What about _.map? Which expects return statements.

If I have a function like _.transform.

Somewhere within the iteratee function I encounter an error; how do I exit from the _.transform function?

i.e.

{
  try {
    fs.readFileSync('dog_pics');
  } catch(e) {
    return;
  }
}

What about _.map? Which expects return statements.

• javascript
• node.js
• lodash

• _.transform requires you to build a new result. Can we see the rest of your iteratee? – Josh C. Commented Aug 20, 2015 at 14:55
• This is a hypothetical. I'm curious if there's a way to jump out of these functions if I need to. – Breedly Commented Aug 20, 2015 at 15:07

2 Answers 2

_.transform callback can return false in order to stop iterating.

From lodash examples:

_.transform([2, 3, 4], function(result, n) {
  result.push(n *= n);
  return n % 2 == 0;
});
// → [4, 9]  

As you can see, iteration breaks on third step, when n === 3

_.map and _.reduce doesn't support iteration stopping

Since _.transform builds a new return object, returning without setting a pushing onto the result would allow you to "jump" out of that iteration.

(I haven't actually tested this code.)