throttle.js•861 B
/**
* Throttle decorator
* @param {Function} fn
* @param {Number} freq
* @return {Function}
*/
function throttle(fn, freq) {
let timestamp = 0;
let threshold = 1000 / freq;
let lastArgs;
let timer;
const invoke = (args, now = Date.now()) => {
timestamp = now;
lastArgs = null;
if (timer) {
clearTimeout(timer);
timer = null;
}
fn.apply(null, args);
}
const throttled = (...args) => {
const now = Date.now();
const passed = now - timestamp;
if ( passed >= threshold) {
invoke(args, now);
} else {
lastArgs = args;
if (!timer) {
timer = setTimeout(() => {
timer = null;
invoke(lastArgs)
}, threshold - passed);
}
}
}
const flush = () => lastArgs && invoke(lastArgs);
return [throttled, flush];
}
export default throttle;