LONDON | MAY 2025 | JESUS DEL MORAL | SPRINT 2 | DATA GROUPS

[delmorallopez]

Sprint 2 Module Data Groups

[cjyuan]

You could also consider the following two approaches for determining if an object contains a property:

  let obj = {}, propertyName = "toString";
  console.log( propertyName in obj );                // true
  console.log( Object.hasOwn(obj, propertyName) );   // false

For more info, you can look up JS "in" operator vs Object.hasOwn.

[delmorallopez]

To check -- Property name (key) exists, we use propertyName in obj or hasOwn(obj, key)
To check -- Property value exists, we use Object.values(obj).includes(value)

const valueExists = Object.values(input).includes(value);
const keyExists = Object.hasOwn(input, value);

return valueExists || keyExists;

[cjyuan]

• Why are these parameters considered invalid?

• Can you make your function return the following expected result?

  // An array is a kind of object, and its keys are its indexes.
  contains(["A", "B", "C"], "1"); // expect false because the first parameter is an array

  // Empty string can also be key
  contains({ "": "Boo" }, "");  // expect true
  
  contains(null, "null"); // expect false even though type of null is equal to "object"

[delmorallopez]

The parameters are considers invalid because "errortest" is not a Key or value fo the object
I added all the tests considering the expected result on your suggestion

function contains(input, value) {
if (
input === null || // explicitly reject null
typeof input !== 'object' ||
Array.isArray(input) ||
value === undefined || value === null // allow empty string
) {
return false;
}

const valueExists = Object.values(input).includes(value);
const keyExists = Object.hasOwn(input, value);

return valueExists || keyExists;

}

[cjyuan]

Changes look good! Well done.

• contains(obj, key) is suppose to just check if the 2nd parameter exists in the first parameter as a key; there is no need to check if the 2nd parameter exists in the first parameter as a value. (No change needed as you already know how to do the checking).