Previous blogpost we discussed extending native data types in JavaScript. Today we’ll create a method in the array prototype that you can use to easily create a range such as an array.
Some programming languages allow you to easily create an array from a range, such as:
Scala
val list = 0 until 10 toList
or Ruby
arr = [0..10]
In JavaScript however, you need to use a for-loop to fill an array with ranged values. You could create a function that returns a filled array based on a from and to value like this:
function fill (from, to) {
var a = [];
for (var i = from; i <= to; i += 1) {
a.push(i);
}
return a;
}
But then you have declared a function fill globally; that doesn’t really say much… it would be syntactically more interesting to use the Array prototype like this:
Array.prototype.fill = function (from, to) {
var a = [];
for (var i = from; i <= to; i += 1) {
a.push(i);
}
return a;
};
Now we can create a new array using a very simple syntax
var arr = [].fill(1,5); // results in [1,2,3,4,5]
While not perfect, defining the fill function this way, is a lot more readable. You start with an empty array and you fill it with a range of values. This makes perfect sense.
