combFilter-1.js

// static Low Pass Feedback Comb Filter
const audioCtx = new AudioContext()
const input = getOsc(audioCtx)
const combFilter = getCombFilter(audioCtx)
const output = audioCtx.destination

input
.connect(combFilter)
.connect(output)

function getCombFilter(audioCtx){
    const node = audioCtx.createGain()
    const lowPass = new BiquadFilterNode(audioCtx, {type: 'lowpass', frequency: 440})
    const delay = new DelayNode(audioCtx, {delayTime: 0.7})
    const gain = audioCtx.createGain()
    gain.gain.setValueAtTime(0.5, audioCtx.currentTime)
    
    node
    .connect(delay)
    .connect(lowPass)
    .connect(gain)
    .connect(node)
    
    return node
}

function getOsc(audioCtx){
    const osc = audioCtx.createOscillator()
    osc.type = 'square'
    osc.frequency.setValueAtTime(440, audioCtx.currentTime) // value in hertz
    osc.start()
    return osc
}