plastiq-throttle

Throttle calls to a function, by arguments, by time, and by promise completion.

example

var throttle = require('plastiq-throttle');

var searchForUsers = throttle(function (query) {
  return http.get('/search?q' + encodeURIComponent(query)).then(function (users) {
    model.users = users;
  });
});

searchForUsers('a');     // GET /search?q=a
searchForUsers('ad');    // -- skip --
searchForUsers('ada');   // -- skip --
searchForUsers('adam');  // GET /search?q=adam

It only calls the function if:

• the arguments are different to the last completed call (compared using ===)
• the promise returned from the last call has completed
• last call was made more than options.throttle milliseconds ago

It will always eventually call the function with the last given arguments.

It is especially useful when synchronising client-side state with server-side resources or CPU intensive operations, some examples:

• fetching search results for a given search string, but only if the search string changes, and not too often.
• fetching an object from a server-side API by ID, but only if the ID changes, and not too often.
• performing a heavy search across client-side data, but only if the criteria changes, and not too often.

Also, because it's intended to be used in plastiq apps, your page will refresh after the function completes (if it's throttled by time, or returns a promise).

api

var throttledFn = throttle([options], fn);
 
function render() {
  throttledFn(arg1, arg2);
 
  return vdom;
}

• options.throttle - the throttle duration in milliseconds, default 140. if 0 then there is no time-based throttling (only based on arguments and promise completion)

• fn - a function to be throttled, if it returns a promise, then the next call will be delayed until this promise completes.

  Why wait for promises to complete? To eliminate the risk of race-conditions. Imagine you search for users matching a first, then adam. If we do them concurrently, then the results for adam could come back before the results of a. model.users will be set to the results of adam first and then finally to the results of a, quite unexpected.

• arg1, arg2, ... - arguments to be passed to fn. If no arguments are passed, then they are considered to be different, that is, the function is potentially executed (considering throttle-time has passed and the previous promise have completed.)

Note that in order to have the page refreshed when a promise completes, or a throttled call is executed, you must call throttledFn inside the render loop, i.e. have plastiq.html.refresh.

reset

throttledFn.reset();

Ensures that the next call to the function will execute, pending throttling and promise returns. Useful if you know that an underlying datasource has changed.