useThrottle

Throttle execution of a function. Especially useful for rate limiting execution of handlers on events like resize and scroll.

useThrottle.js

/* eslint-disable no-undefined,no-param-reassign,no-shadow */

/**
 * Throttle execution of a function. Especially useful for rate limiting
 * execution of handlers on events like resize and scroll.
 *
 * @param {Function} callback -               A function to be executed after delay milliseconds. The `this` context and all arguments are passed through,
 *                                            as-is, to `callback` when the throttled-function is executed.
 *
 * @param {number} delay -                  A zero-or-greater delay in milliseconds. For event callbacks, values around 100 or 250 (or even higher)
 *                                            are most useful.
 *
 * @param {object} [options] -              An object to configure options.
 * @param {boolean} [options.noTrailing] -   Optional, defaults to false. If noTrailing is true, callback will only execute every `delay` milliseconds
 *                                            while the throttled-function is being called. If noTrailing is false or unspecified, callback will be executed
 *                                            one final time after the last throttled-function call. (After the throttled-function has not been called for
 *                                            `delay` milliseconds, the internal counter is reset).
 * @param {boolean} [options.noLeading] -   Optional, defaults to false. If noLeading is false, the first throttled-function call will execute callback
 *                                            immediately. If noLeading is true, the first the callback execution will be skipped. It should be noted that
 *                                            callback will never executed if both noLeading = true and noTrailing = true.
 * @param {boolean} [options.debounceMode] - If `debounceMode` is true (at begin), schedule `clear` to execute after `delay` ms. If `debounceMode` is
 *                                            false (at end), schedule `callback` to execute after `delay` ms.
 *
 * @returns {Function} A new, throttled, function.
 */
export const useThrottle = function(callback, delay, options) {
  const {
    noTrailing = false,
    noLeading = false,
    debounceMode = undefined,
  } = options || {}

  let timeoutID
  let cancelled = false

  // Keep track of the last time `callback` was executed.
  let lastExec = 0

  // Function to clear existing timeout
  function clearExistingTimeout() {
    if (timeoutID)
      clearTimeout(timeoutID)
  }

  // Function to cancel next exec
  function cancel(options) {
    const { upcomingOnly = false } = options || {}
    clearExistingTimeout()
    cancelled = !upcomingOnly
  }

  function wrapper(...arguments_) {
    // eslint-disable-next-line @typescript-eslint/no-this-alias
    const self = this
    const elapsed = Date.now() - lastExec

    if (cancelled)
      return

    // Execute `callback` and update the `lastExec` timestamp.
    function exec() {
      lastExec = Date.now()
      callback.apply(self, arguments_)
    }

    function clear() {
      timeoutID = undefined
    }

    if (!noLeading && debounceMode && !timeoutID)

      exec()

    clearExistingTimeout()

    if (debounceMode === undefined && elapsed > delay) {
      if (noLeading) {
        lastExec = Date.now()
        if (!noTrailing)
          timeoutID = setTimeout(debounceMode ? clear : exec, delay)
      }
      else {
        exec()
      }
    }
    else if (noTrailing !== true) {
      timeoutID = setTimeout(
        debounceMode ? clear : exec,
        debounceMode === undefined ? delay - elapsed : delay,
      )
    }
  }

  wrapper.cancel = cancel

  // Return the wrapper function.
  return wrapper
}