50 lines
1.4 KiB
JavaScript
50 lines
1.4 KiB
JavaScript
var now = require('./now.js');
|
|
|
|
// Returns a function, that, when invoked, will only be triggered at most once
|
|
// during a given window of time. Normally, the throttled function will run
|
|
// as much as it can, without ever going more than once per `wait` duration;
|
|
// but if you'd like to disable the execution on the leading edge, pass
|
|
// `{leading: false}`. To disable execution on the trailing edge, ditto.
|
|
function throttle(func, wait, options) {
|
|
var timeout, context, args, result;
|
|
var previous = 0;
|
|
if (!options) options = {};
|
|
|
|
var later = function() {
|
|
previous = options.leading === false ? 0 : now();
|
|
timeout = null;
|
|
result = func.apply(context, args);
|
|
if (!timeout) context = args = null;
|
|
};
|
|
|
|
var throttled = function() {
|
|
var _now = now();
|
|
if (!previous && options.leading === false) previous = _now;
|
|
var remaining = wait - (_now - previous);
|
|
context = this;
|
|
args = arguments;
|
|
if (remaining <= 0 || remaining > wait) {
|
|
if (timeout) {
|
|
clearTimeout(timeout);
|
|
timeout = null;
|
|
}
|
|
previous = _now;
|
|
result = func.apply(context, args);
|
|
if (!timeout) context = args = null;
|
|
} else if (!timeout && options.trailing !== false) {
|
|
timeout = setTimeout(later, remaining);
|
|
}
|
|
return result;
|
|
};
|
|
|
|
throttled.cancel = function() {
|
|
clearTimeout(timeout);
|
|
previous = 0;
|
|
timeout = context = args = null;
|
|
};
|
|
|
|
return throttled;
|
|
}
|
|
|
|
module.exports = throttle;
|