AudioContext Mute sound when setValueAtTime foreach still working

I have class MorseCodeAudio to create sound for Morse'a code. I'm using window.AudioContext. In my class I have an method with forEach:

morseCode() {
    // irrelevant code

    this.text.split('').forEach(letter => {
        switch(letter) {
            case '.':
                this.gainNode.gain.setValueAtTime(1, this.time)
                this.time += this.period
                this.gainNode.gain.setValueAtTime(0, this.time)
                this.time += this.period
                break
            case '-':
                this.gainNode.gain.setValueAtTime(1, this.time)
                this.time += 3 * this.period
                this.gainNode.gain.setValueAtTime(0, this.time)
                this.time += this.period
                break
            case ' ':
                this.time += 7 * this.period
                break
        }
    })
}

And method to mute sound:

muteAudioMorse(muteValue) {
    if(this.audioCtx.state !== 'closed') this.gainNode.gain.value = muteValue
}

I can't mute the sound because forEach is still executing. If I remove forEach and add one line with sound, like this:

this.gainNode.gain.setValueAtTime(1, 0)

then muteAudioMorse method work correctly.

How I can change gain.value when setValueAtTime from forEach still working?

I "mute" sound by disconnect and connect:

muteAudioMorse(muteValue) {
    if(this.audioCtx.state === 'running') {
        if(muteValue === 0) this.gainNode.disconnect(this.audioCtx.destination)
        else if(muteValue === 1) this.gainNode.connect(this.audioCtx.destination)
    }
}