var array = [1,2,10,14];
const double = []
const newArray = array.forEach((num) => {
double.push(num * 2);
})
Map, Filter, Reduce
Map
`const mapArray = array.map((num) => { return num * 2; })
console.log(mapArray);`
Map is good for use with simple loops in arrays over forEach. The operation with forEach might do nothing. All it cares about is to iterate over a collection of elements. And then apply the operation on each element.
Map has a restriction to the operation. It creates its own array, and returns the results within that new array. To do that with forEach you would need to create an empty array to dump the data into?
With Map it just automatically sets parameters for itself to make the process of adjusting these values easier.
A cleaner version of the above code would look like this:
`const mapArray = array.map(num => num * 2);`
Great principles to have when refactoring code.
Filter
const filterArray = array.filter(num => {
return num > 5
})
This function filters out data within an array based on the parameters of the script. In this case, it ignores anything less than 5, and creates a new array with the two remaining numbers that are greater than 5.
You can apply these to strings, integers, and booleans too probably. Either way, like map it also creates a new array from the data.
Reduce
`const reduceArray = array.reduce((accumulator, num) => { return accumulator + num }, 0);
console.log(reduceArray);`
Accumulator stores information that happens in the body of the function. You set the value at the end of the return function. In this case it is set to 0 and then reduces all the numbers to their combined sum.