Enhancement/use interval

.eslintrc

@@ -7,6 +7,7 @@
     "react-hooks/rules-of-hooks": "error",
     "react-hooks/exhaustive-deps": "warn",
     "react/jsx-filename-extension": 0,
+    "import/prefer-default-export": 0,
     "no-unused-expressions": [ 2,{
       "allowShortCircuit": true,
     }],

demo/components/UseTimerDemo.js

@@ -13,8 +13,7 @@ export default function UseTimerDemo({ expiryTimestamp }: Object) {
     pause,
     resume,
     restart,
-  } = useTimer({ expiryTimestamp, onExpire: () => console.warn('onExpire called') });
-
+  } = useTimer({ expiryTimestamp, autoStart: true, onExpire: () => console.warn('onExpire called') });
 
   return (
     <div>

readme.md

@@ -33,7 +33,7 @@ function MyTimer({ expiryTimestamp }) {
     pause,
     resume,
     restart,
-  } = useTimer({ expiryTimestamp, onExpire: () => console.warn('onExpire called') });
+  } = useTimer({ expiryTimestamp, autoStart: true, onExpire: () => console.warn('onExpire called') });
 
 
   return (
@@ -73,8 +73,10 @@ export default function App() {
 | key | Type | Required | Description |
 | --- | --- | --- | ---- |
 | expiryTimestamp | number(timestamp) | YES | this will define for how long the timer will be running   |
+| autoStart | boolean | No | flag to decide if timer should start automatically |
 | onExpire | Function | No | callback function to be executed once countdown timer is expired |
 
+
 ### Values
 
 | key | Type | Description |

src/hooks/index.js

@@ -0,0 +1,5 @@
+import useInterval from './useInterval';
+
+export {
+  useInterval,
+};

src/hooks/useInterval.js

@@ -0,0 +1,21 @@
+import { useEffect, useRef } from 'react';
+
+export default function useInterval(callback, delay) {
+  const callbacRef = useRef();
+
+  // update callback function with current render callback that has access to latest props and state
+  useEffect(() => {
+    callbacRef.current = callback;
+  });
+
+  useEffect(() => {
+    if (!delay) {
+      return () => {};
+    }
+
+    const interval = setInterval(() => {
+      callbacRef.current && callbacRef.current();
+    }, delay);
+    return () => clearInterval(interval);
+  }, [delay]);
+}

src/useStopwatch.js

@@ -1,48 +1,28 @@
-import { useState, useEffect, useRef } from 'react';
+import { useState } from 'react';
 import { Time } from './utils';
+import { useInterval } from './hooks';
 
-export default function useStopwatch(settings) {
-  const { autoStart, offsetTimestamp } = settings || {};
-
+export default function useStopwatch({ autoStart, offsetTimestamp }) {
   const [seconds, setSeconds] = useState(Time.getSecondsFromExpiry(offsetTimestamp || 0));
   const [isRunning, setIsRunning] = useState(autoStart);
-  const intervalRef = useRef();
 
-  function clearIntervalRef() {
-    if (intervalRef.current) {
-      setIsRunning(false);
-      clearInterval(intervalRef.current);
-      intervalRef.current = undefined;
-    }
-  }
+  useInterval(() => {
+    setSeconds((prevSeconds) => (prevSeconds + 1));
+  }, isRunning ? 1000 : null);
 
   function start() {
-    if (!intervalRef.current) {
-      setIsRunning(true);
-      intervalRef.current = setInterval(() => setSeconds((prevSeconds) => (prevSeconds + 1)), 1000);
-    }
+    setIsRunning(true);
   }
 
   function pause() {
-    clearIntervalRef();
+    setIsRunning(false);
   }
 
   function reset(offset: number) {
-    clearIntervalRef();
+    setIsRunning(autoStart);
     setSeconds(Time.getSecondsFromExpiry(offset || 0));
-    if (autoStart) {
-      start();
-    }
   }
 
-  // didMount effect
-  useEffect(() => {
-    if (autoStart) {
-      start();
-    }
-    return clearIntervalRef;
-  }, []);
-
   return {
     ...Time.getTimeFromSeconds(seconds), start, pause, reset, isRunning,
   };

src/useTime.js

@@ -1,31 +1,13 @@
-import { useState, useEffect, useRef } from 'react';
+import { useState } from 'react';
 import { Time } from './utils';
+import { useInterval } from './hooks';
 
-export default function useTime(settings) {
-  const { format } = settings || {};
-
+export default function useTime({ format }) {
   const [seconds, setSeconds] = useState(Time.getSecondsFromTimeNow());
-  const intervalRef = useRef();
-
-  function clearIntervalRef() {
-    if (intervalRef.current) {
-      clearInterval(intervalRef.current);
-      intervalRef.current = undefined;
-    }
-  }
-
-  function start() {
-    if (!intervalRef.current) {
-      intervalRef.current = setInterval(() => setSeconds(Time.getSecondsFromTimeNow()), 1000);
-    }
-  }
-
-  // didMount effect
-  useEffect(() => {
-    start();
-    return clearIntervalRef;
-  }, []);
 
+  useInterval(() => {
+    setSeconds(Time.getSecondsFromTimeNow());
+  }, 1000);
 
   return {
     ...Time.getFormattedTimeFromSeconds(seconds, format),

src/useTimer.js

@@ -1,89 +1,61 @@
-import { useState, useEffect, useRef } from 'react';
+import { useState } from 'react';
 import { Time, Validate } from './utils';
+import { useInterval } from './hooks';
 
-export default function useTimer(settings) {
-  const { expiryTimestamp: expiry, onExpire } = settings || {};
+const DEFAULT_DELAY = 1000;
+export default function useTimer({ expiryTimestamp: expiry, onExpire, autoStart }) {
   const [expiryTimestamp, setExpiryTimestamp] = useState(expiry);
   const [seconds, setSeconds] = useState(Time.getSecondsFromExpiry(expiryTimestamp));
-  const [isRunning, setIsRunning] = useState(true);
-  const intervalRef = useRef();
-
-  function clearIntervalRef() {
-    if (intervalRef.current) {
-      setIsRunning(false);
-      clearInterval(intervalRef.current);
-      intervalRef.current = undefined;
-    }
-  }
+  const [isRunning, setIsRunning] = useState(autoStart);
+  const [didStart, setDidStart] = useState(autoStart);
+  const extraMilliSeconds = Math.floor((seconds - Math.floor(seconds)) * 1000);
+  const [delay, setDelay] = useState(extraMilliSeconds > 0 ? extraMilliSeconds : 1000);
 
   function handleExpire() {
-    clearIntervalRef();
     Validate.onExpire(onExpire) && onExpire();
-  }
-
-  function start() {
-    if (!intervalRef.current) {
-      setIsRunning(true);
-      intervalRef.current = setInterval(() => {
-        const secondsValue = Time.getSecondsFromExpiry(expiryTimestamp);
-        if (secondsValue <= 0) {
-          handleExpire();
-        }
-        setSeconds(secondsValue);
-      }, 1000);
-    }
+    setIsRunning(false);
+    setDelay(null);
   }
 
   function pause() {
-    clearIntervalRef();
+    setIsRunning(false);
   }
 
-  function resume() {
-    if (!intervalRef.current) {
-      setIsRunning(true);
-      intervalRef.current = setInterval(() => setSeconds((prevSeconds) => {
-        const secondsValue = prevSeconds - 1;
-        if (secondsValue <= 0) {
-          handleExpire();
-        }
-        return secondsValue;
-      }), 1000);
-    }
-  }
-
-  function restart(newExpiryTimestamp) {
-    clearIntervalRef();
+  function restart(newExpiryTimestamp, newAutoStart) {
+    const secondsValue = Time.getSecondsFromExpiry(newExpiryTimestamp);
+    const extraMilliSecondsValue = Math.floor((secondsValue - Math.floor(secondsValue)) * 1000);
+    setDelay(extraMilliSecondsValue > 0 ? extraMilliSecondsValue : 1000);
+    setDidStart(newAutoStart);
+    setIsRunning(newAutoStart);
     setExpiryTimestamp(newExpiryTimestamp);
+    setSeconds(secondsValue);
   }
 
-  function handleExtraMilliSeconds(secondsValue, extraMilliSeconds) {
-    setIsRunning(true);
-    intervalRef.current = setTimeout(() => {
-      const currentSeconds = Time.getSecondsFromExpiry(expiryTimestamp);
-      setSeconds(currentSeconds);
-      if (currentSeconds <= 0) {
-        handleExpire();
-      } else {
-        intervalRef.current = undefined;
-        start();
-      }
-    }, extraMilliSeconds);
+  function resume() {
+    const time = new Date();
+    time.setMilliseconds(time.getMilliseconds() + (seconds * 1000));
+    restart(time, true);
   }
 
-  useEffect(() => {
-    if (Validate.expiryTimestamp(expiryTimestamp)) {
-      const secondsValue = Time.getSecondsFromExpiry(expiryTimestamp);
-      const extraMilliSeconds = Math.floor((secondsValue - Math.floor(secondsValue)) * 1000);
-      setSeconds(secondsValue);
-      if (extraMilliSeconds > 0) {
-        handleExtraMilliSeconds(secondsValue, extraMilliSeconds);
-      } else {
-        start();
-      }
+  function start() {
+    if (didStart) {
+      setSeconds(Time.getSecondsFromExpiry(expiryTimestamp));
+      setIsRunning(true);
+    } else {
+      resume();
     }
-    return clearIntervalRef;
-  }, [expiryTimestamp]);
+  }
 
+  useInterval(() => {
+    if (delay !== DEFAULT_DELAY) {
+      setDelay(DEFAULT_DELAY);
+    }
+    const secondsValue = Time.getSecondsFromExpiry(expiryTimestamp);
+    setSeconds(secondsValue);
+    if (secondsValue <= 0) {
+      handleExpire();
+    }
+  }, isRunning ? delay : null);
 
   return {
     ...Time.getTimeFromSeconds(seconds), start, pause, resume, restart, isRunning,