A JavaScript implementation of the Python's range()
function.
npm i python-range
import range from 'python-range';
const r = range(10);
console.log(r); // range(0, 10, 1)
console.log(Array.from(r)); // [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
console.log(r[3]); // 3
console.log(r.length); // 10
console.log(Array.from(range(2, 5))); // [2, 3, 4]
console.log(Array.from(range(5, 0, -1))); // [5, 4, 3, 2, 1]
const r = range(3, 6);
for (const n of r) {
console.log(n); // logs 3, 4 and 5
}
r.forEach(n => console.log(n)); // logs 3, 4, and 5
Unlike other range modules, python-range
has lazy evaluation.
See Why is “1000000000000000 in range(1000000000000001)” so fast in Python 3?
console.log(range(1000000000000001).includes(1000000000000000)); // true
console.log(range(0, 100000000000001, 10).includes(100000000000000)); // true
console.log(range(0, -1000000000, -3)[12345678]); // -37037034
python-range
exports two values: a PythonRange
class, and a range
function (a default export), which returns a PythonRange
object.
import range, {PythonRange} from 'python-range';
console.log(range(10) instanceof PythonRange); // true
The PythonRange
constructor creates a range starting with start
(inclusive) and ending with stop
(exclusive). The step
parameter defaults to 1
and specifies the distance between two elements. The step
parameter must be different than 0
.
When called with only one argument, the start
parameter defaults to 0
and the passed argument becomes stop
.
const r = range(3);
console.log(r.start); // 0
console.log(r.stop); // 3
You can access range elements using array indices. Note that this requires native Proxy
support.
const r = range(2, 5);
console.log(r[0]); // 2
console.log(r[2]); // 4
The PythonRange
constructor creates these properties based on the arguments passed to the constructor, or the default values. These properties are writable, and changing them automatically updates the range.
const r = range(5);
console.log(Array.from(r)); // [0, 1, 2, 3, 4]
r.step = 2;
console.log(Array.from(r)); // [0, 2, 4]
The length
property specifies the number of elements in the range. It's updated automatically when the start
, stop
and step
properties are changed.
const r = range(5);
console.log(r.length); // 5
r.stop = 3;
console.log(r.length); // 3
Works the same as accessing numeric properties (e.g. r[2]
). Use this method if you want to execute your code in environments without native Proxy
support.
console.log(range(2, 5).get(1)); // 3
Executes the callback
once for each element with element, current index and the range as arguments. Works the same as Array.prototype.forEach()
.
Returns true
if the range contains the specified value; otherwise returns false
.
console.log(range(3, 5).includes(3)); // true
console.log(range(10).includes(10)); // false
Returns the smallest value in the range.
console.log(range(10).min()); // 0
console.log(range(0, -15, -1).min()); // -14
Returns the largest value in the range.
console.log(range(10).max()); // 9
console.log(range(12, 0, -2).max()); // 12
Reverses the range in-place and returns it.
console.log(range(2, 5).reverse()); // range(4, 1, -1)
console.log(range(10, 0, -1).reverse()); // range(1, 11, 1)
Returns a string range(<start>, <stop>, <step>)
, where <start>
, <stop>
and <step>
are the start
, stop
and step
properties of the range.
console.log(String(range(3, 6, 2))); // range(3, 6, 2)
Returns the result of the toString()
method.
Returns the result of calling Array.prototype.values()
on the range.
Returns true
if the passed arguments are equal; otherwise returns false
. Two ranges are considered equals if they contain the same set of values. For example, range(3, 3)
and range(0)
are equal, because they're both empty ranges. range(4, 5, 2)
and range(4, 6, 3)
are equal too, because they both contain only one element: 4
.
const r = range(3);
console.log(PythonRange.areEqual(r, r)); // true
console.log(PythonRange.areEqual(range(10), range(10))); // true
console.log(PythonRange.areEqual(range(3, 3), range(0))); // true, because both ranges are empty
console.log(PythonRange.areEqual(range(4, 5, 2), range(4, 6, 3))); // true, because both ranges contain only one element: 4
console.log(PythonRange.areEqual(range(2), range(3))); // false
Returns an instance of PythonRange
with the specified arguments.
In order to be able to access numeric properties (e.g. r[2]
), native Proxy
support is required (see compatibility table). If you want to execute your code in environments without Proxy
support, you can use the get()
method instead.