How to check if every property on object is the same recursively in JavaScript?

Let’s say, we are required to write a function, say isSame() that accepts a nested object and returns a boolean depending on the fact whether or not all the keys have the same values. When saying all the keys we mean all the last keys like if a key has a nested object as its value, we are required to traverse to the end of the nested object and check for that value.

For example − If the object is −

const obj = {
   a: 1,
   b: 1,
   c: {
      aa: 1
   }
};

Then the function should return true as all the end keys have the same value (1). Therefore, let’s write a recursive solution to this problem.

Example

const obj = {
   a: 1,
   b: 1,
   c: {
      aa: 3
   }
};
const allSame = (obj, value) => {
   const keys = Object.keys(obj);
   for(let i = 0; i < keys.length; i++){
      if(typeof obj[keys[i]] === "object" &&
      !Array.isArray(obj[keys[i]])){
         return allSame(obj[keys[i]], value);
      };
      if(!value){
         value = obj[keys[i]];
         continue;
      }
      if(obj[keys[i]] !== value){
         return false;
      };
   };
   return true;
}
console.log(allSame(obj));
console.log(allSame({ a: 1, b: 1, c: { aa: 1 } }));
console.log(allSame({ a: { x: 1 }, b: 1, c: { aa: 1 } }));
console.log(allSame({ a: 1, b: 1, c: { aa: 2 } }));

Output

The output in the console will be −

false
true
true
false