losslessThrottle.js

var _ = require('lodash');

function losslessThrottle(func, wait) {
  var scheduledCalls = [];
  return function() {
    // Add a timestamp to `scheduledCalls` signifying when the current invocation will take place.
    // The last element of `scheduledCalls` will be the timestamp of the latest scheduled invocation, so the current
    // invocation should occur `wait` milliseconds after that.
    var scheduledTimestamp = _.max([_.last(scheduledCalls) + wait, _.now()]);
    scheduledCalls.push(scheduledTimestamp);
    return _.delay(func.bind(this), scheduledTimestamp - _.now(), arguments);
  };
}

_.mixin({losslessThrottle: losslessThrottle});

// ---

function myFunc() { console.log('called'); }
var throttled = _.losslessThrottle(myFunc, 1000);
throttled();
throttled();
throttled();
// (prints 'called' once at time=0, once at time=1, and once at time=2)