This tiny library allows the nth number of ordinal numbers like in the css syntax of the nth-child pseudo selector.

Examples

Get nth number of index

NthNumber.get('2n', 0)   // 0
NthNumber.get('2n', 1)   // 2
NthNumber.get('2n+1', 0) // 1
NthNumber.get('2n+1', 1) // 3

Check nth

NthNumber.isNth('2n', 10) // true
NthNumber.isNth('2n', 11) // false

Get list of nth number

NthNumber.list('3n', 0, 10)   // [0, 3, 6, 9] 
NthNumber.list('3n+1', 0, 10) // [1, 4, 7]

Loop

NthNumber.for('3n', 0, 10, (num) => console.log(num))
// 0
// 3
// 6
// 9 

await NthNumber.pFor('3n+1', 0, 10, async (num) => console.log(num))
// 1
// 4
// 7

Use instance

const nthNumber = new NthNumber('3n+2')

nthNumber.get(100)  // 302
nthNumber.isNth(31) // false
nthNumber.isNth(32) // true
nthNumber.for(0, 10, (num) => console.log(num))
// 2
// 5
// 8 
await nthNumber.pFor(0, 10, async (num) => console.log(num))
// 2
// 5
// 8 

Template

pattern: ^\d*n([\+|\-]\d+)?$

In the template, the multiplier must be larger than the offset.

6n+3 - correct

6n+30 - incorrect