froebel/throttle.mjs

TypeScript utility library

const {
  performance
} = "performance" in globalThis ? globalThis : {performance:{now:()=>Date.now()}};
export const cancel = Symbol("throttle.cancel");
/**
 * Create a throttled function that invokes `fun` at most every `ms` milliseconds.
 *
 * `fun` is invoked with the last arguments passed to the throttled function.
 *
 * Calling `[throttle.cancel]()` on the throttled function will cancel the currently
 * scheduled invocation.
 */

const throttle = Object.assign((fun, ms, {
  leading = true,
  trailing = true
} = {}) => {
  let toId;
  let lastInvoke = -Infinity;
  let lastArgs;

  const invoke = () => {
    lastInvoke = performance.now();
    toId = undefined;
    fun(...lastArgs);
  };

  return Object.assign((...args) => {
    if (!leading && !trailing) return;
    lastArgs = args;
    const dt = performance.now() - lastInvoke;
    if (dt >= ms && toId === undefined && leading) invoke();else if (toId === undefined && trailing) {
      toId = setTimeout(invoke, dt >= ms ? ms : ms - dt);
    }
  }, {
    [cancel]: () => clearTimeout(toId)
  });
}, {
  cancel
});
export default throttle;