forEach is returning undefined

Question

I want my foreach() to loop through an array of maps and check if the type value matches. If not return the else statement.

Function

function checkCars(carData) {
        const cars = carData.models;

        models.forEach(model => {
            if (model.type === 'Toyota' || model.type === 'Hyundai') {
                return "Type A";
            } else {
                return "Type B";
            }
        });
    }

Database

"models": [
  {type: "Toyota"}
  {type: "Hyundai"}
  {type: "Audi"}
  {type: "VW"}
]

Answer 1

The return value of Array.prototype.forEach() is undefined , you can not return anything explicitly from forEach() .

You can try with Array.prototype.map() instead:

The map() method creates a new array populated with the results of calling a provided function on every element in the calling array.

function checkCars(carData) {
  const cars = carData.models;

  return models.map(model => {
    if (model.type === 'Toyota' || model.type === 'Hyundai') {
      return "Type A";
    } else {
      return "Type B";
    }
  });
}

Answer 2

forEach has no return value. You should use map function to change the element's types.

Answer 3

If you want to transform the array, you want map :

function checkCars(carData) {
  const cars = carData.models;

  return models.map(model => {
    if (model.type === 'Toyota' || model.type === 'Hyundai') {
      return "Type A";
    } else {
      return "Type B";
    }
  });
}

Answer 4

You can use something like this:

function checkCars(carData) {
        const cars = carData.models;
        let type = "Type A"
        models.forEach(model => {
            if (model.type !== 'Toyota' && model.type !== 'Hyundai') {
                type = "Type B";
            }
        });
        return type
    }