CODEWITHSUNDEEP
javascripttypescriptfindecmascript-2017
Joan
Joan

Reputation: 243

JS: Handle with find() property undefined

I have a method which returns a value from an element in the array. Not all the elements have the property I want to return. I would like to do this function with one line using the method find(). I've tried this way to solve it: 

getExecsFromTour(tourId){
 return this.repInfo.find(el => el.id == tourId ).execs || [];
}

But the elements which don't contain the property execs return an error of undefined.

To solve it, I had to store the result in a local variable: 

getExecsFromTour(tourId){
    let items       = this.repInfo.find(el => el.id == tourId);
    return items    != undefined ? items.execs : [];
}

But I would like to know if I am missing something and this function can be achieved with one sentence.

Upvotes: 10

Views: 21407

Answers (2)

fedeghe
fedeghe

Reputation: 1318

what about 

getExecsFromTour(tourId){
     return this.repInfo.find(el => 'execs' in el && el.id == tourId ).execs || [];
}

...

EDITED

var a = [{execs : 1, id:4}, {id:5}];
function getExecsFromTour(tourId, x){
    return (x = a.find(el => 'execs' in el && el.id == tourId )) ? x.execs : [];
}

this time at least I ran it couple of times

Upvotes: -1

DCtheTall
DCtheTall

Reputation: 196

You seem to have the general idea, Array.prototype.find will search the array for the first element which, when used as an argument of the callback, will have the callback return a truthy value. If nothing is found, it returns undefined.

Your code should work, but yes, one way to do it in one line (if you want) is to use:

getExecsFromTour(tourId){
  return (this.repInfo.find(el => el.id == tourId) || {}).execs || [];
}

If Array.prototype.find returns undefined, the first inner parenthetical expression will be evaluated to empty object, which can attempt (and fail) to access the .execs key without a TypeError, which will also evaluate to undefined, in which case the function returns empty array, which is what your code above does.

EDIT: Someone commented this solution already, lol, but as the comments say, nothing wrong with keeping it multiline (more readable that way).

Upvotes: 14

Related Questions