series

Create a number sequence from the start value to the end value, incremented by the specified step.

Basic Usage

import { series } from 'radash'

const numbers = series(1, 5)
// [1, 2, 3, 4, 5]

const evenNumbers = series(0, 10, 2)
// [0, 2, 4, 6, 8, 10]

Syntax

function series(
  start: number,
  end: number,
  step?: number
): number[]

Parameters

• start (number): The starting value of the sequence
• end (number): The ending value of the sequence
• step (number, optional): Step size, default is 1

Return Value

Returns an array of numbers from start to end, incremented by step.

Examples

Basic Sequence

import { series } from 'radash'

console.log(series(1, 5))      // [1, 2, 3, 4, 5]
console.log(series(0, 3))      // [0, 1, 2, 3]
console.log(series(-2, 2))     // [-2, -1, 0, 1, 2]
console.log(series(5, 1))      // [5, 4, 3, 2, 1] (auto-decrement)

Specify Step

import { series } from 'radash'

console.log(series(0, 10, 2))   // [0, 2, 4, 6, 8, 10]
console.log(series(1, 10, 2))   // [1, 3, 5, 7, 9]
console.log(series(0, 10, 3))   // [0, 3, 6, 9]
console.log(series(10, 0, -2))  // [10, 8, 6, 4, 2, 0]

Negative Number Sequence

import { series } from 'radash'

console.log(series(-5, -1))     // [-5, -4, -3, -2, -1]
console.log(series(-10, -1, 2)) // [-10, -8, -6, -4, -2]
console.log(series(-1, -5))     // [-1, -2, -3, -4, -5]

Decimal Sequence

import { series } from 'radash'

console.log(series(0, 1, 0.2))  // [0, 0.2, 0.4, 0.6, 0.8, 1]
console.log(series(1, 2, 0.25)) // [1, 1.25, 1.5, 1.75, 2]
console.log(series(0.1, 0.5, 0.1)) // [0.1, 0.2, 0.3, 0.4, 0.5]

Empty Sequence

import { series } from 'radash'

console.log(series(5, 1, 1))    // [] (cannot increment to target)
console.log(series(1, 5, -1))   // [] (cannot decrement to target)
console.log(series(1, 1))       // [1] (start equals end)

Use in Loops

import { series } from 'radash'

// Iterate over the sequence
for (const i of series(1, 5)) {
  console.log(`Iteration ${i}`)
}

// Output:
// Iteration 1
// Iteration 2
// Iteration 3
// Iteration 4
// Iteration 5

Create Index Array

import { series } from 'radash'

const indices = series(0, 4)
console.log(indices) // [0, 1, 2, 3, 4]

// For array operations
const fruits = ['apple', 'banana', 'cherry', 'date', 'elderberry']
const fruitIndices = series(0, fruits.length - 1)

fruitIndices.forEach(index => {
  console.log(`${index}: ${fruits[index]}`)
})

Create Matrix Indices

import { series } from 'radash'

const rows = series(0, 2)
const cols = series(0, 3)

// Create indices for a 3x4 matrix
for (const row of rows) {
  for (const col of cols) {
    console.log(`Position [${row}, ${col}]`)
  }
}

Generate Test Data

import { series } from 'radash'

// Generate user IDs
const userIds = series(1, 10)
console.log(userIds) // [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

// Generate price range
const prices = series(10, 100, 10)
console.log(prices) // [10, 20, 30, 40, 50, 60, 70, 80, 90, 100]

// Generate timestamps
const timestamps = series(Date.now(), Date.now() + 86400000, 3600000) // One per hour

Use with map

import { series } from 'radash'

// Create an array of objects
const users = series(1, 5).map(id => ({
  id,
  name: `User ${id}`,
  email: `user${id}@example.com`
}))

console.log(users)
// [
//   { id: 1, name: 'User 1', email: 'user1@example.com' },
//   { id: 2, name: 'User 2', email: 'user2@example.com' },
//   { id: 3, name: 'User 3', email: 'user3@example.com' },
//   { id: 4, name: 'User 4', email: 'user4@example.com' },
//   { id: 5, name: 'User 5', email: 'user5@example.com' }
// ]

Create Repeating Patterns

import { series } from 'radash'

// Create alternating booleans
const alternating = series(0, 9).map(i => i % 2 === 0)
console.log(alternating) // [true, false, true, false, true, false, true, false, true, false]

// Create repeating colors
const colors = ['red', 'green', 'blue']
const colorPattern = series(0, 9).map(i => colors[i % colors.length])
console.log(colorPattern) // ['red', 'green', 'blue', 'red', 'green', 'blue', 'red', 'green', 'blue', 'red']

Notes

1. Includes End Value: The sequence includes the end value
2. Auto Direction: If start > end and step is positive, a negative step is used automatically
3. Empty Sequence: If the end value cannot be reached with the given step, returns an empty array
4. Floating-Point Precision: Floating-point operations may have precision issues
5. Performance: For large sequences, consider memory usage

Differences from Other Methods

• Array.from({length: n}, (_, i) => i): Can only start from 0
• [...Array(n).keys()]: Can only go from 0 to n-1
• series(): Can specify any start and end value, as well as step

Practical Application Scenarios

1. Pagination: Generate page number sequences
2. Test Data: Generate test ID sequences
3. Charts: Generate axis ticks
4. Loops: Replace for-loop indices
5. Matrix Operations: Generate matrix indices