AudioParam: setTargetAtTime() 方法

setTargetAtTime(target, startTime, timeConstant)

// create audio context
const audioCtx = new AudioContext();

// set basic variables for example
const myAudio = document.querySelector("audio");

const atTimePlus = document.querySelector(".at-time-plus");
const atTimeMinus = document.querySelector(".at-time-minus");

// Create a MediaElementAudioSourceNode
// Feed the HTMLMediaElement into it
const source = audioCtx.createMediaElementSource(myAudio);

// Create a gain node and set its gain value to 0.5
const gainNode = audioCtx.createGain();
gainNode.gain.value = 0.5;
let currGain = gainNode.gain.value;

// connect the AudioBufferSourceNode to the gainNode
// and the gainNode to the destination
source.connect(gainNode);
gainNode.connect(audioCtx.destination);

// set buttons to do something onclick
atTimePlus.onclick = () => {
  currGain = 1.0;
  gainNode.gain.setTargetAtTime(1.0, audioCtx.currentTime + 1, 0.5);
};

atTimeMinus.onclick = () => {
  currGain = 0;
  gainNode.gain.setTargetAtTime(0, audioCtx.currentTime + 1, 0.5);
};