Use static getters for echo params

src/lib/audio/audio-effects.js

@@ -38,7 +38,7 @@ class AudioEffects {
         this.playbackRate = 1;
         switch (name) {
         case effectTypes.ECHO:
-            sampleCount = Math.max(sampleCount, Math.floor((this.trimEndSeconds + 0.75) * buffer.sampleRate));
+            sampleCount = Math.max(sampleCount, Math.floor((this.trimEndSeconds + EchoEffect.TAIL_SECONDS) * buffer.sampleRate));
             break;
         case effectTypes.FASTER:
             this.playbackRate = pitchRatio;
@@ -115,7 +115,7 @@ class AudioEffects {
                 this.adjustedTrimStartSeconds, this.adjustedTrimEndSeconds));
             break;
         case effectTypes.ECHO:
-            ({input, output} = new EchoEffect(this.audioContext, 0.25,
+            ({input, output} = new EchoEffect(this.audioContext,
                 this.adjustedTrimStartSeconds, this.adjustedTrimEndSeconds));
             break;
         case effectTypes.ROBOT:

src/lib/audio/effects/echo-effect.js

@@ -1,7 +1,12 @@
 class EchoEffect {
-    constructor (audioContext, delayTime, startTime, endTime) {
+    static get DELAY_TIME () {
+        return 0.25;
+    }
+    static get TAIL_SECONDS () {
+        return 0.75;
+    }
+    constructor (audioContext, startTime, endTime) {
         this.audioContext = audioContext;
-        this.delayTime = delayTime;
         this.input = this.audioContext.createGain();
         this.output = this.audioContext.createGain();
 
@@ -12,7 +17,7 @@ class EchoEffect {
         this.effectInput.gain.setValueAtTime(0, endTime);
 
         this.delay = this.audioContext.createDelay(1);
-        this.delay.delayTime.value = delayTime;
+        this.delay.delayTime.value = EchoEffect.DELAY_TIME;
         this.decay = this.audioContext.createGain();
         this.decay.gain.value = 0.3;