Recursive Contains

recursive_contains.js

// solution to problem #6 in recursive exercises
function contains(object, searchValue) {
  // because `null` has a typof "object", we have to explicitly check
  // to prevent trying to access `null`'s values (which don't exist)
  if (typeof object !== "object" || object === null) {
    return object === searchValue;
  }

  for (const value of Object.values(object)) {
    // An important problem in the code quiz solution is that `return contains()` will only
    // search the first property of an object, as it will return whatever the result for it is.
    // If our value was nested within the second property, for example, it would never get checked
    // even if the first nested object did not contain it.
    if (contains(value, searchValue)) {
      return true;
    }
  }
  return false;
}

Came up with this function myself:

function contains(obj, targetVal) {
  for (const currentVal of Object.values(obj)) {
    if (typeof currentVal === "object") {
      return contains(currentVal, targetVal);
    }
    if (currentVal === targetVal) return true;
  }
  return false;
}

Felt quite good about it even though I knew that a null could very easily render it useless. But then I realised that I could just change the third line to: if (typeof currentVal === "object" && currentVal !== null) { to prevent that from happening.

I thought I needed to search for the keys and values:

function contains(obj, item) {
if (Object.values(obj).length === 0) return false;
else if (item in obj || Object.values(obj).includes(item)) return true;
else {
for (let value of Object.values(obj)) {
return contains(value, item);
}
}
}

Here is a more improved answer that even runs for flat objects as well as nested ones.

The provided first code doesn't check directly the equality of the value; it directly jump to nested, leaving the flat object unchecked
here is the improved code

function contains(object, searchValue) {
    if (typeof object !== "object" || object === null) {
        return object === searchValue;
    }

    for (const value of Object.values(object)) {
        // First check direct equality
        if (value === searchValue) {
            return true;
        }

        // Then check nested objects
        if (typeof value === "object" && value !== null) {
            if (contains(value, searchValue)) {
                return true;
            }
        }
    }
    return false;
}

OR

function contains(object, searchValue) {
  // Handle non-objects
  if (typeof object !== "object" || object === null) {
    return object === searchValue;
  }

  // Check all values
  for (const value of Object.values(object)) {
    // Direct match OR recursive match
    if (value === searchValue || contains(value, searchValue)) {
      return true;
    }
  }
  return false;
}

Unless I'm missing something, the given solution in the original post works with flat objects just fine @kazeneza-zephilin

Your solution is also more repetitive, effectively adding the exact same guard check twice. This might have some marginal performance gains by avoiding new stack frames in certain contexts, but I think it's unlikely to be meaningful.