An ES6 implementation of the debounce function. "Debouncing enforces that a function not be called again until a certain amount of time has passed without it being called. As in 'execute this function only if 100 milliseconds have passed without it being called.'" - CSS-Tricks (https://css-tricks.com/the-difference-between-throttling-and-debounc…

debounce.js

function debounce(callback, wait, immediate = false) {
  let timeout = null 
  
  return function() {
    const callNow = immediate && !timeout
    const next = () => callback.apply(this, arguments)
    
    clearTimeout(timeout)
    timeout = setTimeout(next, wait)

    if (callNow) {
      next()
    }
  }
}

/** 
 * Normal event
 * event      | |      |
 * time     ----------------
 * callback   | |      |
 *
 * Call log only when it's been 100ms since the last sroll
 * scroll     | |      |
 * time     ----------------
 * callback         |      | 
 *              |100|  |100|
 */

const handleScroll = debounce((arg, event) => {
  console.log(`${arg} ${event.type}`)
}, 100, true)

window.addEventListener('scroll', (event) => {
  handleScroll('Event is:', event)
})

@BjornLuG arrow functions have implicit context binding, it's "bound" to the context of the containing scope.. or inherits it? Semantics.

If the function passed into the debounce has it's context already bound to this, then the arrow function calling it will allow it to will maintain it's original context bindings.

Below, using my pure debounce, I can bind the this to the function being debounced:

({
  namespace: function() {
    const functionCall = function() {console.log('this: ', this)}
    setTimeout(debounce(functionCall.bind(this), 1000))
  }
}).namespace()

Without the bind, this will be whatever the parent scope is for the debounce function itself.

Alternatively, passing in a pure function doesn't require a binding at all, as this will be appropriately bound:

({
  namespace: function() {
    const functionCall = () => console.log('this: ', this)
    setTimeout(debounce(functionCall), 1000))
  }
}).namespace()

@jpenney1 I understand your example completely and I've tested my debounce function with your example, which works fine too. But I found a specific case on Reddit which your function fails.

Case:

const obj = {
  name: 'foo',
  sayMyName() {
    console.log('My name is', this.name)
  }
}

obj.sayMyName() //-> My name is foo
obj.deb = debounce(obj.sayMyName, 1000)
obj.deb() // Should log -> My name is foo

With your function, obj is not binded to your callback and will return My name is. So unless I explicitly bind the function:

obj.deb = debounce(obj.sayMyName.bind(obj), 1000)
obj.deb()

This will now log correctly. But the problem is that the explicit binding is somewhat unnatural, and the debounce function should handle it automatically for us.
With my function however, it logs correctly even without the explicit binding, outputting My name is foo.

I've done some extensive testing and so far only this test case had me scratching my head. I hope i'm not missing anything out here.

Cheers!

Works great! Thank you!

@jpenney1 I understand your example completely and I've tested my debounce function with your example, which works fine too. But I found a specific case on Reddit which your function fails.

Case:

const obj = {
  name: 'foo',
  sayMyName() {
    console.log('My name is', this.name)
  }
}

obj.sayMyName() //-> My name is foo
obj.deb = debounce(obj.sayMyName, 1000)
obj.deb() // Should log -> My name is foo

With your function, obj is not binded to your callback and will return My name is. So unless I explicitly bind the function:

obj.deb = debounce(obj.sayMyName.bind(obj), 1000)
obj.deb()

This will now log correctly. But the problem is that the explicit binding is somewhat unnatural, and the debounce function should handle it automatically for us.
With my function however, it logs correctly even without the explicit binding, outputting My name is foo.

I've done some extensive testing and so far only this test case had me scratching my head. I hope i'm not missing anything out here.

Cheers!

This help me a lot.