Use JSOneshotClosure in JSTimer

Author: kateinoigakukun

Diff for: IntegrationTests/TestSuites/Sources/PrimaryTests/main.swift

@@ -488,21 +488,29 @@ try test("Date") {
 }
 
 // make the timers global to prevent early deallocation
-var timeout: JSTimer?
+var timeouts: [JSTimer] = []
 var interval: JSTimer?
 
 try test("Timer") {
     let start = JSDate().valueOf()
     let timeoutMilliseconds = 5.0
-
+    var timeout: JSTimer!
     timeout = JSTimer(millisecondsDelay: timeoutMilliseconds, isRepeating: false) {
         // verify that at least `timeoutMilliseconds` passed since the `timeout` timer started
         try! expectEqual(start + timeoutMilliseconds <= JSDate().valueOf(), true)
     }
+    timeouts += [timeout]
+
+    timeout = JSTimer(millisecondsDelay: timeoutMilliseconds, isRepeating: false) {
+        fatalError("timer should be cancelled")
+    }
+    timeout = nil
 
     var count = 0.0
     let maxCount = 5.0
     interval = JSTimer(millisecondsDelay: 5, isRepeating: true) {
+        // ensure that JSTimer is living
+        try! expectNotNil(interval)
         // verify that at least `timeoutMilliseconds * count` passed since the `timeout` 
         // timer started
         try! expectEqual(start + timeoutMilliseconds * count <= JSDate().valueOf(), true)

Diff for: Sources/JavaScriptKit/BasicObjects/JSTimer.swift

@@ -14,7 +14,7 @@ public final class JSTimer {
   /// Indicates whether this timer instance calls its callback repeatedly at a given delay.
   public let isRepeating: Bool
 
-  private let closure: JSClosure
+  private let closure: JSOneshotClosure
 
   /** Node.js and browser APIs are slightly different. `setTimeout`/`setInterval` return an object
   in Node.js, while browsers return a number. Fortunately, clearTimeout and clearInterval take
@@ -34,9 +34,16 @@ public final class JSTimer {
     - callback: the closure to be executed after a given `millisecondsDelay` interval.
   */
   public init(millisecondsDelay: Double, isRepeating: Bool = false, callback: @escaping () -> ()) {
-    closure = JSClosure { _ in
-        callback()
-        return .undefined
+    if isRepeating {
+        closure = JSClosure { _ in
+            callback()
+            return .undefined
+        }
+    } else {
+        closure = JSOneshotClosure { _ in
+            callback()
+            return .undefined
+        }
     }
     self.isRepeating = isRepeating
     if isRepeating {