once.js•1 kB
// It's actually "debounce"
"use strict";
var isValue = require("es5-ext/object/is-value")
, callable = require("es5-ext/object/valid-callable")
, nextTick = require("next-tick")
, validTimeout = require("./valid-timeout");
var apply = Function.prototype.apply;
module.exports = function (fn/*, timeout*/) {
var scheduled, run, context, args, delay, timeout = arguments[1], handle;
callable(fn);
if (isValue(timeout)) {
timeout = validTimeout(timeout);
delay = setTimeout;
} else {
delay = nextTick;
}
run = function () {
if (!scheduled) return; // IE8 tends to not clear immediate timeouts properly
scheduled = false;
handle = null;
apply.call(fn, context, args);
context = null;
args = null;
};
return function () {
if (scheduled) {
if (!isValue(handle)) {
// 'nextTick' based, no room for debounce
return;
}
clearTimeout(handle);
}
scheduled = true;
context = this;
args = arguments;
handle = delay(run, timeout);
};
};