CODEWITHSUNDEEP
javascriptarraysecmascript-6
CodeFinity
CodeFinity

Reputation: 1350

Why is filter not giving same results as push with for..of iteration?

I have extracted an array of objects, from the following raw data: https://gist.githubusercontent.com/Miserlou/c5cd8364bf9b2420bb29/raw/2bf258763cdddd704f8ffd3ea9a3e81d25e2c6f6/cities.json

Suffice to say, the data looks something like this:

[0 … 99] 0 : city : "New York" growth_from_2000_to_2013 : "4.8%" latitude : 40.7127837 longitude : -74.0059413 population : "8405837" rank : "1" state : "New York" proto : Object 1 : {city: "Los Angeles", growth_from_2000_to_2013: "4.8%", latitude: 34.0522342, longitude: -118.2436849, population: "3884307", …}

I've stored this as const JSON_LOCS, referenced in the code below.

I'm trying to filter this down looking for cities that include some specific test. I've approached it 2 different ways. One way seems to work, but Array.prototype.filter() doesn't.

const test = [];
      for (let t of JSON_LOCS) {
        if (t.city.includes('las')) {
          test.push(t);
        }
      }

      const test2 = JSON_LOCS.filter(loc => { // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/filter
        loc.city.includes('las');
      });
      console.log(test); // Yields a couple of results
      console.log(test2); // Always empty! :(

Upvotes: 0

Views: 44

Answers (2)

Mayday
Mayday

Reputation: 5136

remove the { }

const test2 = JSON_LOCS.filter(loc => { // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/filter
  loc.city.includes('las');
});

into

const test2 = JSON_LOCS.filter(loc => // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/filter
  loc.city.includes('las'); // When not wrapped into {} it assumes its the return statement
);

Upvotes: 1

mostafa tourad
mostafa tourad

Reputation: 4388

Instead of this line 

oc.city.includes('las');

write this line 

return oc.city.includes('las');

you simply forget the return statement which in this case will return undefined

Upvotes: 1

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