> Uncaught TypeError: Cannot read property 'reduce' of undefined MyAwesomeArray.forEach(x => x * x).reduce((total, value) => total + value) That's something you can't do with forEach() because, as you might guess, it returns undefined. This means that you can attach reduce(), sort(), filter() and so on after performing a map() method on an array. The second difference between these array methods is the fact that map() is chainable. Even if they do the same job, the returning value remains different. The forEach() method returns undefined and map() returns a new array with the transformed elements. The first difference between map() and forEach() is the returning value. MyAwesomeArray.forEach(element => console.log(element.name)) However, instead of returning a new array like map, it returns undefined. Like map, the forEach() method receives a function as an argument and executes it once for each array element. It will always return the same number of items. This means that it returns a new array that contains an image of each element of the array. Then it applies it on each element and returns an entirely new array populated with the results of calling the provided function. The map method receives a function as a parameter. In this article, we'll look at the following: Because they both do an iteration and output something. The two most commonly used for iteration are () and ().īut I think that they remain a little bit unclear, especially for a beginner. JavaScript has some handy methods which help us iterate through our arrays.

For each in kotlin