How to check if a JSON Array object contains a Key

Question

{
 "myJSONArrayObject": [
 {
 "12": {}
 },
 {
 "22": {}
 }
 ]
} 

I have the above JSON Array object. How can I check if myJSONArrayObject has a particular key?

This approach is not working :

let myIntegerKey = 12;
if (myJSONArrayObject.hasOwnProperty(myIntegerKey))
 continue;

It seems to return false when it contains a key and true when it doesn't.

• Shilly: If it's possible, maybe you can use regular objects, so [{ "id": 12, "value": {} }, { "id": 22, "value": {} }]. Way easier to search/transform than when every object inside the array has different keys.

Answer 1

myJSONArrayObject is an array. It doesn't have 12 as a property (Unless there are 12+ items in the array)

So, check if some of the objects in the array have myIntegerKey as a property

const exists = data.myJSONArrayObject.some(o => myIntegerKey in o)

or if myIntegerKey is always an own property

const exists = data.myJSONArrayObject.some(o => o.hasOwnProperty(myIntegerKey))

Here's a snippet:

const data={myJSONArrayObject:[{"12":{}},{"22":{}}]},
 myIntegerKey = 12,
 exists = data.myJSONArrayObject.some(o => myIntegerKey in o);
console.log(exists)

• Nimrod Yanai: This is great! Is there a way to check not just the key, but a key:value pairing with this method?

Answer 2

"myJSONArrayObject" is an array so you have to check hasOwnProperty on each of it's elements:

let myIntegerKey = 12;
for (var obj in myJSONArrayObject) {
 console.log(obj.hasOwnProperty(myIntegerKey));
}

Answer 3

The most direct method to retrieve the object by a key is to use JavaScript bracket notation. Use the find method to iterate over the array, also.

const obj = {
 myJSONArrayObject: [{
 12: {},
 },
 {
 22: {},
 },
 ],
};
const myIntegerKey = 12;
const myObject = obj.myJSONArrayObject.find(item => item[myIntegerKey]);
console.log("exists", myObject !== undefined);

Answer 4

const obj = {
 myJSONArrayObject: [
 {
 12: {},
 },
 {
 22: {},
 },
 ],
};
const myIntegerKey = '12';
const isExist = obj.myJSONArrayObject.findIndex((f) => { return f[myIntegerKey]; }) > -1;
console.log(isExist); 

You can make it faster with every()

const obj = {
 myJSONArrayObject: [
 {
 22: {},
 },
 {
 12: {},
 },
 ],
};
const myIntegerKey = '12';
const isExist = !obj.myJSONArrayObject
 .every((f) => {
 return !f[myIntegerKey];
 });
console.log(isExist); 

Note: Here the key name (12: {},) doesn't rely on typeof myIntegerKey, 12 and '12' both will return true.

• Shilly: Misunderstood your comment, thought you meant the other way around, that it Does matter sometimes and using this code prevents it.