The `flatMap()` method is just like `flat()` except that it passes each value through a mapping function before flattening the result, and only is capable of flattening a two-dimensional array.
Basically, it’s like first calling the `map()` method on an array and then call the `flat()` method on the result array.
Array flatMap() Syntax:
array.flatMap(function(currentValue, index, arr), thisValue)
Array flatMap() Method Parameters:
The `find()` method takes two arguments.
The first argument is a reference to a function. For each element in the target array, the flatMap() method will call the reference function and pass an element to be mapped in the target reference function.
This function takes 3 arguments:
- The first argument is the element in the array.
- The second argument is the index of that element.
- The third argument is a reference to the target array.
Inside this function, we specify a set of instructions that will be executed for each element in the array. These instructions are mainly related to mapping the target element to produce a new one and return that as a result.
Other than the function, the `flatMap()` method takes a second argument as well. This second argument, which is optional, is a reference to an object that will bind to the `this` keyword in the target function that we passed as the first argument.
Array flatMap() Method Return Value:
The method doesn’t change the original array and instead it’ll return a single-dimensional array with the values of the target multidimensional array all mapped and set as its elements.
const arr = [1,2,3,4,5,6,7,8,9]; const flatten = arr.flatMap(value=>[value, value*10]); console.log(flatten);
[1, 10, 2, 20, 3, 30, 4, 40, 5, 50, 6, 60, 7, 70, 8, 80, 9, 90]