Removing elements from array based on existence of a key value

Question

I have an object that I have converted to an array using this

convertToArray(data: any) {
  let arr = [];
  Object.keys(data).map(function(key){
     arr.push(data[key]);
  });
  return arr;
}

Here is the result

{0: {…}, 1: {…}, 2: {…}, hideTitle: false, template: "football-news", customProperties: {…}}
0: {NewsID: 90, AnotherAttribute: 5, …}
1: {NewsID: 90, AnotherAttribute: 5, …}
2: {NewsID: 90, AnotherAttribute: 5, …}
customProperties: {template: "list-view"}
hideTitle: false
template: "news"
__proto__: Object

to

(6) [{…}, {…}, {…}, false, "football-news", {…}]
0: {NewsID: 90, AnotherAttribute: 5, …}
1: {NewsID: 90, AnotherAttribute: 5, …}
2: {NewsID: 90, AnotherAttribute: 5, …}
3: false
4: "news"
5: {template: "list-view"}
length: 6
__proto__: Array(0)

I want to remove any items (arr.pop or filter) that DOESNT have a NewsID key.

I appreciate any help in advance :)

Do you want me to copy 200 lines of JSON in here?, I dont mind, but the jJSONon itself isn't my problem, I took a screenshot to help to understand — John Mersal, Feb 15 '19 at 01:28
You can create a dummy data mate, no need of posting your full json. this will help people to answer quickly and accurately — Code Maniac, Feb 15 '19 at 01:30

Nick Parsons · Accepted Answer · 2019-12-05T12:34:18.380

You can use .filter() with destructuring assignment to filter out values which are undefined by only keeping objects where the NewsID gives a truthy value (here NewsID will be undefined if it does not exist, and thus falsey).

Moreover, you can refine your convertToArray method by using Object.values(). There is no need to loop over your keys/values twice.

See working example below:

function convertToArray(data) {
  return Object.values(data);
}

const myObj = {
  0: {
    NewsID: 90,
    AnotherAttribute: 5
  },
  1: {
    NewsID: 90,
    AnotherAttribute: 5
  },
  2: {
    NewsID: 90,
    AnotherAttribute: 5
  },
  customProperties: {
    template: "list-view"
  },
  hideTitle: false,
  template: "news"
},
arr = convertToArray(myObj),

res = arr.filter(({NewsID}) => NewsID);
console.log(res);

Note:

If your NewsID can be 0 then you should check using .filter(({NewsID}) => NewsID !== undefined).
If your NewsID can have an explicit value of undefined (eg: you use {NewsID: undefined}) you should use .filter((obj) => obj instanceof Object && "NewsID" in obj)

Nick i guess you don't need `NewsID !== undefined`, +1 for explanation — Code Maniac, Feb 15 '19 at 01:45

score 0 · Answer 2 · answered Feb 15 '19 at 01:32

I might have misunderstood your question because printouts as images are really hard to read.

So it looks like you have a list of objects and you want to remove ones that don't have a certain key, correct?

You can it in following manner:

result = arr.filter(obj => "NewsID" in obj)

If you want to learn more about how to check if an object has a key, this looks like good place to start: Checking if a key exists in a JavaScript object?

score 0 · Answer 3 · answered Feb 15 '19 at 01:47

Use a simple Boolean filter upon Object.values of the object:

const data = {
  0: {
    NewsID: 90,
    AnotherAttribute: 5
  },
  1: {
    NewsID: 90,
    AnotherAttribute: 5
  },
  2: {
    NewsID: 90,
    AnotherAttribute: 5
  },
  customProperties: {
    template: "list-view"
  },
  hideTitle: false,
  template: "news"
};

const arr = Object.values(data).filter(({ NewsID }) => NewsID);

console.log(arr);

score 0 · Answer 4 · answered Feb 15 '19 at 01:55

You have an array which has values of diffrent types and diffrent types of object. First you need to check whether value in array is instance of a object or not.

function convertToArray(data) {
  let arr = [];
  Object.keys(data).map(function(key){
     arr.push(data[key]);
  });
  return arr;
}
var obj = {
   0:  { NewsID: 90, AnotherAttribute: 5},
   1: {NewsID: 90, AnotherAttribute: 5}, 
   2: {NewsID: 90, AnotherAttribute: 5}, 
   hideTitle: false, 
   template: "football-news", customProperties: {template: "list-view"}
};
var arr = convertToArray(obj);
var filterarr = arr.filter(a => a instanceof Object && ("NewsID" in a));
console.log(filterarr);

score 0 · Answer 5 · answered Feb 15 '19 at 08:49

Try this :

var arr = [
  {NewsID: 90, AnotherAttribute: 5},
  {NewsID: 90, AnotherAttribute: 5},
  {NewsID: 90, AnotherAttribute: 5},
  false,
  "football-news",
  {template: "list-view"}
];

var result = arr.filter(item => item instanceof Object && ("NewsID" in item));
console.log(result);

Removing elements from array based on existence of a key value

5 Answers5