求JavaScript中NSTimer的等效实现：支持延迟执行、取消与重置

Hey there! If you're coming from iOS development and need an NSTimer-like tool in JavaScript, we can build a flexible wrapper that hits all your requirements: delayed code execution, on-demand cancellation, and interval resets. Here's a robust, easy-to-use solution:

This class mimics NSTimer's core behavior, using JavaScript's built-in setTimeout/setInterval under the hood while adding the control you need:

class Timer {
  constructor(callback, delay, isRepeating = false) {
    this.callback = callback;
    this.delay = delay;
    this.isRepeating = isRepeating;
    this.timerId = null;
    this._start();
  }

  // Internal method to start the timer
  _start() {
    if (this.isRepeating) {
      this.timerId = setInterval(() => {
        this.callback();
      }, this.delay);
    } else {
      this.timerId = setTimeout(() => {
        this.callback();
        // Auto-cleanup for one-time timers
        this.timerId = null;
      }, this.delay);
    }
  }

  // *Equivalent to NSTimer's `invalidate()`*: Cancel the timer immediately
  invalidate() {
    if (this.timerId) {
      this.isRepeating ? clearInterval(this.timerId) : clearTimeout(this.timerId);
      this.timerId = null;
    }
  }

  // Reset the timer with a new delay (uses original delay if no new value is provided)
  reset(newDelay = this.delay) {
    // Cancel existing timer first
    this.invalidate();
    // Update delay if a new one is passed
    this.delay = newDelay;
    // Restart the timer
    this._start();
  }
}

How to Use It #

Let's walk through examples matching your use cases:

1. Execute Code After a Specified Interval #

Create a one-time timer (just like NSTimer with repeats: NO):

// Fire a function after 2 seconds
const oneTimeTimer = new Timer(() => {
  console.log("One-time timer triggered!");
}, 2000);

// Cancel it anytime before it fires (uncomment to test)
// oneTimeTimer.invalidate();

2. Cancel Execution On-Demand #

Use the invalidate() method to stop a repeating or pending timer:

// Repeat a function every 1 second
const repeatingTimer = new Timer(() => {
  console.log("Repeating timer tick!");
}, 1000, true);

// Cancel the timer after 5 seconds
setTimeout(() => {
  repeatingTimer.invalidate();
  console.log("Repeating timer cancelled successfully");
}, 5000);

3. Reset the Timer's Interval #

Update the delay and restart the timer with reset():

const timer = new Timer(() => {
  console.log("Timer fired!");
}, 3000);

// After 1 second, reset the timer to fire after 5 seconds instead
setTimeout(() => {
  timer.reset(5000);
  console.log("Timer reset to 5-second delay");
}, 1000);

Key Details #

• Safe Cancellation: Calling invalidate() on a timer that's already fired or cancelled does nothing—no errors to worry about, just like NSTimer.
• Memory Management: The class clears timer references when cancelled or completed, avoiding unintended memory leaks.
• Flexibility: Works for both one-time and repeating timers, just like NSTimer.

内容的提问来源于stack exchange，提问作者Kishoretheju