CODEWITHSUNDEEP
javascriptfunction
Ben Aston
Ben Aston

Reputation: 55749

Word for type of function that short-circuits a result until a specific call-gap has elapsed

I need a function f that when applied to function g, passes through the first call, then short-circuits subsequent calls until the time between subsequent calls is greater than a value.

In plain English: if calls to f come in like a "machine gun" I want a memoized value to be used, otherwise normal operation should occur.

Is there a word for this kind of function modifier?

var g = () => { /*...*/ };
var h = f(g); // is there an idiomatic term for function `f`
// `h` is now effectively limiting calls through to g

Edit:

Current hacked implementation (untested, doesn't support functions with parameters):

function memoizeByRate(fn, options) {
	var lastCallTime = 0, result;
	return function() {
		var now = +Date.now(), tmpResult;
		if((now - lastCallTime) > options.lifetime) {
			tmpResult = fn.apply(this, arguments);
			if(options.test && options.test(tmpResult)) {
				lastCallTime = now; // !
				result = tmpResult;
			}
		}
		lastCallTime = now;
		return result;
	};
}

// "Test harness"
var i = 0;
var f = () => { console.log('call', ++i); }
var g = memoizeByRate(f, { lifetime: 1000 });

g()
g()
g()
setTimeout(g, 1000);

Upvotes: 0

Views: 40

Answers (2)

Bergi
Bergi

Reputation: 664648

This is called debouncing, in your case with execution of the debounced function on the leading edge. However, that term is usually used for side-effectful functions only, so no result will be returned or even stored, you'll want to add the term memoisation (as you already did). I guess I'd go for debounceWithCache or memoiseInBursts.

See What does _.debounce do? and Debouncing and Throttling Explained Through Examples for details.

Upvotes: 1

Sergio Tulentsev
Sergio Tulentsev

Reputation: 230396

In underscore.js terms, this is called throttle.

Upvotes: 0

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