Problem statement:

We have a number of functions in our web application that are getting called too frequently. We'd like you to create a function that, given a function and a time interval, returns a new function that we can call as often as we like, but ensures that the original function is never called more than once per interval.

Example usage:

limitedDoSomething = rateLimit(doSomething, 500);

Now calls to limitedDoSomething will simply call doSomething, but never more than once every 500 milliseconds.

Test Cases:

function logHello(){ // just a sample function
  console.log('Hello!'); 
}

limitedDoSomething = rateLimit(logHello, 500);

limitedDoSomething(); // should log “Hello!”

window.setTimeout(function(){
  limitedDoSomething();  // should not log “Hello!"
}, 400);

window.setTimeout(function(){
  limitedDoSomething();  // should log “Hello!"  
}, 500);

My solution:

function rateLimit(func, limit){
  var lastInvokedTimestamp;

  return function(){
    if(typeof lastInvokedTimestamp === 'undefined' || Date.now() - lastInvokedTimestamp >= limit){
      lastInvokedTimestamp = Date.now();
      console.log('go ahead!');
      return func();
    } else {
      console.log('too early!');
      return;
    }
  };

}

// run test cases
function logHello(){ // just a sample function
  console.log('Hello!'); 
}

limitedDoSomething = rateLimit(logHello, 500);

limitedDoSomething(); // should log “Hello!”

window.setTimeout(function(){
  limitedDoSomething();  // should not log “Hello!"
}, 400);

window.setTimeout(function(){
  limitedDoSomething();  // should log “Hello!"  
}, 500);

Equivalent jsBin

I would love to know if there is a way to improve my solution.

Problem statement:

We have a number of functions in our web application that are getting called too frequently. We'd like you to create a function that, given a function and a time interval, returns a new function that we can call as often as we like, but ensures that the original function is never called more than once per interval.

Example usage:

limitedDoSomething = rateLimit(doSomething, 500);

Now calls to limitedDoSomething will simply call doSomething, but never more than once every 500 milliseconds.

Test Cases:

function logHello(){ // just a sample function
  console.log('Hello!'); 
}

limitedDoSomething = rateLimit(logHello, 500);

limitedDoSomething(); // should log “Hello!”

window.setTimeout(function(){
  limitedDoSomething();  // should not log “Hello!"
}, 400);

window.setTimeout(function(){
  limitedDoSomething();  // should log “Hello!"  
}, 500);

My solution:

function rateLimit(func, limit){
  var lastInvokedTimestamp;

  return function(){
    if(typeof lastInvokedTimestamp === 'undefined' || Date.now() - lastInvokedTimestamp >= limit){
      lastInvokedTimestamp = Date.now();
      console.log('go ahead!');
      return func();
    } else {
      console.log('too early!');
      return;
    }
  };

}

// run test cases
function logHello(){ // just a sample function
  console.log('Hello!'); 
}

limitedDoSomething = rateLimit(logHello, 500);

limitedDoSomething(); // should log “Hello!”

window.setTimeout(function(){
  limitedDoSomething();  // should not log “Hello!"
}, 400);

window.setTimeout(function(){
  limitedDoSomething();  // should log “Hello!"  
}, 500);

Equivalent jsBin

I would love to know if there is a way to improve my solution.