CODEWITHSUNDEEP
javascript
shanky
shanky

Reputation: 801

Filter out undefined property

I'm iterating over markers array and trying to filter out those places whose opening hours is undefined, however, I'm unable to filter out the undefined data. Below is my code and result: 

const markers = data.map(place => {
      if (typeof place. opening_now != 'undefined') {
        return {
          position: place.geometry.location,
          content: place.name,
          key: place.id,
          opening_now: place.opening_now
        };
      }

(20) [undefined, {…}, {…}, undefined, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}, {…}]

0:undefined

1:{position: _.F, content: "San Francisco Marriott Union Square", key: "c904f2aae3fb8743f27bce36da94753a19b02131", opening_now : {open_now: true, weekday_text: Array(0)}}

2:{position: _.F, content: "Cornell Hotel De France", key: "547ceb15210b70b8734500183410bb10c644c395", opening_now :{open_now: true, weekday_text: Array(0)}}

3:undefined

4:{position: _.F, content: "San Francisco Marriott Marquis", key: "f007d2f91c0070ebdfec60275baa33623f0b771b", opening_now: {…}}

5:{position: _.F, content: "La Mar Cebicheria Peruana", key: "2dfcc4cf449104804f979d0c74583f2b3a48d046", opening_now: {…}}..

Upvotes: 0

Views: 180

Answers (4)

Andy
Andy

Reputation: 63524

The reason why you're getting undefineds in your output data is that map operates on each element in the array. If your array is 10 elements long, your output array will also be 10 elements long. In your example you're just returning undefined (ie "no object") when your opening_hours is undefined.

The map() method creates a new array with the results of calling a provided function on every element in the calling array.

So the filter solution is quite tidy. It works the same as map but only returns the elements that satisfy the condition you give the function.

ES6

const markers = data.filter(place => place.opening_now.open_now)

ES5 (which you might be more used to)

var markers = data.filter(function (place) {
  return place.opening_now.open_now;
});

It removes the undefined gaps in the array that you appear to have. This example, because you don't specifically express undefined also removes instances of opening hours equalling null if that's your bag.

DEMO

Upvotes: 2

Roman
Roman

Reputation: 5210

Instead of map() you can use filter(). filter() works like map() but instead of transforming values it will filter values by an boolean. If a condition returns false it will leave it out.

Code

const makers = data.filter(place => place.opening_hours)

If place.opening_hours is undefined it will be convert into a false and filter() will leave this value out.

Upvotes: 0

jdubjdub
jdubjdub

Reputation: 613

first filter for defined objects, then for entries with opening hours.

const markers = data.filter((i) => i).filter((j) => j.opening_hours);

Upvotes: 0

Jarek Kulikowski
Jarek Kulikowski

Reputation: 1389

If you are only returning object elements from data then this should work:

const markers = data.filter(
    place => typeof place.opening_hours != 'undefined'
);

Upvotes: 0

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