Remove object that have an empty array value

Question

So I have an object inside a json file like this:

{
 "0": {
 "damage_type": "Scratch",
 "regions": []
 },
 "1": {
 "damage_type": "Dent",
 "regions": []
 },
 "2": {
 "damage_type": "Dent",
 "regions": [
 "front side",
 "front window"
 ]
 }
}

What I am trying to accomplish is to remove the object that have empty regions. Like this:

{
 "2": {
 "damage_type": "Dent",
 "regions": [
 "front side",
 "front window"
 ]
 }
}

I am using a for loop and still unsuccessful:

jsonfile.readFile(theJsonFile, function (err, obj) {
 if (err) console.error(err)
 for (var i = 0; i <= Object.keys(obj).length - 1; i++) {
 if (obj[i].damage_type.length < 1) {
 delete obj[i]
 } 
 }
}

Any ideas?

• Ateş Göral: You're checking for the length of damage_type, not regions.

Answer 1

Calling the parsed value damages instead of obj, you can grab all entries as key/value pairs, iterate over them and remove no-region "damages" by their ids:

Object.entries(damages).forEach(([id, damage]) => {
 if (!damage.regions.length) {
 delete damages[id];
 }
});

Alternatively, you can create a brand new structure without touching the original structure:

const entries = Object.entries(damages);
const filteredEntries = entries.filter(([_, damage]) => damage.regions.length);
const filteredDamages = Object.fromEntries(filteredEntries);

Answer 2

In this case first you need an array. To convert object to arrays use entry entry

let obj = {
 "0": {
 "damage_type": "Scratch",
 "regions": []
 },
 "1": {
 "damage_type": "Dent",
 "regions": []
 },
 "2": {
 "damage_type": "Dent",
 "regions": [
 "front side",
 "front window"
 ]
 }
}

converting array :

const myentry= Object.entries(obj);

Now the best way to eliminate or filter array is to use filter method and in return get the other object which have filter value.

Filter

const myFiletrObj = myentry.filter(([_, obj]) => obj.regions.length).reduce(withObjectAssign, {})
function withObjectAssign(object, [key, value]) {
 return Object.assign(object, {[key]: value})
}

This will give you filtered output.

Answer 3

made changes, try this

let json = {
 "0": {
 "damage_type": "Scratch",
 "regions": []
 },
 "1": {
 "damage_type": "Dent",
 "regions": []
 },
 "2": {
 "damage_type": "Dent",
 "regions": [
 "front side",
 "front window"
 ]
 }
};
function walk(obj) {
 for (var key in obj) {
 let length = Object.keys(obj[key].regions).length; // get the length
 if(length==0){
 delete obj[key];
 
 }
 }
 console.log(json);
}
walk(json);

output

{ '2':
 { damage_type: 'Dent',
 regions: [ 'front side', 'front window' ]
 } 
}

• Praveen Kumar: @hisam if this is what you looking for, please upvote.

Answer 4

You can delete a json node by its key

var json = { ... };
var key = "foo";
delete json[key]; // Removes json.foo from the dictionary.

• Ateş Göral: The OP already seems to know how to delete a property. (Also, a nitpick: Don't name a JS data structure json unless it actually contains a JSON-stringified value. In your case, you're better off calling it data, obj, value, etc.)

Answer 5

Why your code is not working?

You are incorrectly checking the condition for damage_type.length from each node. You need to delete the nodes with empty regions. So you have to check for regions.length.

Your working Solution

const obj = { 
 "0": { "damage_type": "Scratch", "regions": [] },
 "1": { "damage_type": "Dent", "regions": [] },
 "2": { "damage_type": "Dent", "regions": [ "front side", "front window" ] }
};
for (var i = 0; i < Object.keys(obj).length; i++) {
 if (!obj[i].regions || obj[i].regions.length === 0) {
 delete obj[i]
 } 
}
console.log(obj);

This solution works only because that the key of objects are same as the index "0", "1" and "2". If the key is something else, this wont work.

Corrected solution

Get the keys using Object.keys and delete the correct node.

Working Fiddle

const obj = { 
 "0": { "damage_type": "Scratch", "regions": [] },
 "1": { "damage_type": "Dent", "regions": [] },
 "2": { "damage_type": "Dent", "regions": [ "front side", "front window" ] }
};
const keys = Object.keys(obj);
for (var i = 0; i <= keys.length - 1; i++) {
 if (!obj[keys[i]].regions || obj[keys[i]].regions.length === 0) {
 delete obj[keys[i]]
 } 
}
console.log(obj);

Generic Solution

Get the key value combination using Object.entries

const obj = { 
 "0": { "damage_type": "Scratch", "regions": [] },
 "1": { "damage_type": "Dent", "regions": [] },
 "2": { "damage_type": "Dent", "regions": [ "front side", "front window" ] }
};
const entries = Object.entries(obj);
entries.forEach(([key, value]) => {
 if (!value.regions || value.regions.length === 0) {
 delete obj[key]
 }
})
console.log(obj);

• Ateş Göral: You probably want Object.entries(data) to use the actual keys. With your example, it's just luck that the values will be indexed the same way as the original object's keys.
• Nitheesh: Yeah Object.entries(data) or Object.keys will do the trick irrespective of the values for key.
• Ateş Göral: Calling data[key] twice is still sub-par to using Object.entries() to get both the key and value at the same time. Also, the OP doesn't seem to have a need to check if the regions property exists.
• Nitheesh: @AtesGoral agreed Updated the answer with Object.entries(). OP needs to delete nodes with empty region. So the regions key needs to be validated for the delete condition