Omitting optional else-branches
When the if-branch already returns, we can omit the keyword else. The execution will only go beyond the if-branch if it doesn’t apply anyways.
Read fire tipConditionally modifying array elements
If we want to change only the values in an array that match a condition, we can combine Array.prototype.map() with a ternary operator. By putting these in a function, we can quickly apply this pattern to many different scenarios.
// takes an array, a function that checks each element, and another function
// that it applies to every element that the check returns `true` for
const mapMatches = (array, checkFunction, changeFunction) =>
array.map(element => checkFunction(element) ? changeFunction(element) : element)
// change every name that contains an “e” into uppercase
mapMatches(
['Leo', 'Paul', 'Joe', 'Fred', 'Sam'],
name => name.includes('e'),
name => name.toUpperCase()
)
// ⇒ ['LEO', 'Paul', 'JOE', 'FRED', 'Sam'],
// divide every even number by two
mapMatches(
[4, 8, 15, 16, 23, 42],
number => number % 2 === 0,
number => number / 2
)
// ⇒ [2, 4, 15, 8, 23, 21]