Given an object how can I get the name used to describe it?

Question

I have a JSON object( mainObj ) which in turn has objects (say obj1 , obj2 , obj3 ). What I am trying to achieve is when I check for a condition iterating through every obj in the mainObj and if it holds true, I want to add only the name of that obj in an array of String. Something like,

for(obj in mainObj){
 if(obj holds condition){
    add the descriptor of the obj (in string format) to an array (not the entire obj)
 }

Answer 1

You can use Object.keys() to iterate over your object keys, then use Array.filter() to filter the keys, here I am checking if the inner objects have a property show and if this property is truthy:

 const mainObj = { obj1: { show: true, a: 1 }, obj2: { show: false, a: 2 }, obj3: { a: 3 }, obj4: { show: true, b: 1 } }; const result = Object.keys(mainObj).filter(key => mainObj[key].show); console.log(result); 

If you want to use a for-in loop, you have to make sure the property is part of the object and is not inherited from its protype chain using Object.hasOwnProperty() :

 const mainObj = { obj1: { show: true, a: 1 }, obj2: { show: false, a: 2 }, obj3: { a: 3 }, obj4: { show: true, b: 1 } }; const result = []; for (const prop in mainObj) { if (mainObj.hasOwnProperty(prop) && mainObj[prop].show) { result.push(prop); } } console.log(result);