add init value for semaphore

index.js

@@ -37,6 +37,7 @@ var __generator = (this && this.__generator) || function (thisArg, body) {
 };
 var Semaphore = (function () {
     function Semaphore(initialValue) {
+        if (initialValue === void 0) { initialValue = 1; }
         this.value = initialValue;
         this.queue = [];
     }

index.test.js

@@ -0,0 +1,18 @@
+const semaphore = require('./index.js')
+
+const { V, P } = semaphore(2)
+
+const fn = async i => {
+  console.log('wait', i)
+  await P()
+  console.log('enter', i)
+  setTimeout(() => {
+    console.log('leave', i)
+    V()
+  }, 1000)
+}
+
+fn(1)
+fn(2)
+fn(3)
+fn(4)