Periodic waveform functions. Phase t is normalized to [0, 1] — one full turn.
npm install periodic-function
import { sine, square, wavetable } from 'periodic-function' sine(0.25) // 1 (peak) square(0.75) // -1 (low) wavetable(null, [0, 1, 0, 0.5]) // Float32Array wavetable from Fourier coefficients
All functions take phase t ∈ [0, 1] as first argument. Values outside [0, 1] wrap correctly.
| Function | Description | |
|---|---|---|
| Waveforms | ||
 |
sine(t, phase=0) |
Sine wave. phase=0.25 gives cosine. |
 |
cosine(t, phase=0) |
Cosine wave. Equivalent to sine(t, 0.25). |
 |
sawtooth(t) |
Descending ramp: 1 at t=0, −1 approaching t=1. For ascending ramp use triangle(t, 0). |
 |
square(t, duty=0.5) |
Square wave. duty = fraction of period spent high. |
 |
triangle(t, ratio=0.5) |
Triangle wave. ratio = peak position (0 = ascending ramp, 1 = descending ramp). |
 |
trapezoid(t, p1=0.25, p2=0.5, p3=0.75) |
Trapezoid wave. Rise ends at p1, fall starts at p2, fall ends at p3. Generalizes square and triangle. |
 |
pulse(t, width=0) |
Dirac-like pulse: 1 at t=0, 0 elsewhere. width extends the high region. |
 |
clausen(t, harmonics=10) |
Clausen function: Σ sin(kθ)/k². |
 |
noise(t) |
Periodic noise — repeating random buffer. |
| Fourier / Wavetable | ||
 |
fourier(t, real, imag) |
Evaluate one sample from Fourier coefficients. real[k] and imag[k] are cosine/sine amplitudes for harmonic k. Index 0 is DC, 1 is fundamental. |
 |
wavetable(real, imag, {size=8192, normalize=true}) |
Build a Float32Array wavetable from Fourier coefficients. Used for AudioContext.createPeriodicWave. |
| Lookup | ||
 |
interpolate(t, samples) |
Linearly interpolate between samples, treating them as one period. |
 |
step(t, samples) |
Step lookup — nearest sample, no interpolation. |
// Cosine as a phase-shifted sine sine(0, 0.25) // 1 (same as cosine(0)) // Square wave with 10% duty cycle square(0.05, 0.1) // 1 square(0.15, 0.1) // -1 // Triangle with peak at 0.25 (asymmetric) triangle(0.25, 0.25) // -1 (valley, since peak is at t=0) // Trapezoid as a square with soft edges trapezoid(t, 0.05, 0.5, 0.55) // Fourier series: pure sine fourier(0.25, null, [0, 1]) // 1 // Wavetable for Web Audio API PeriodicWave const real = new Float32Array(64) const imag = new Float32Array(64) for (let k = 1; k < 64; k += 2) imag[k] = 4 / (Math.PI * k) // square wave const table = wavetable(real, imag) // Float32Array[8192], normalized to ±1
- web-audio-api — uses
wavetable()forPeriodicWave - MDN: createPeriodicWave
- List of periodic functions
MIT © Dmitry Iv