Rate limit a javascript function

Most of the other proposed solutions here evenly space the function calls using an interval or recursive function with a timeout.

This interpretation of your question doesn't really do what I believe you're asking for, because it requires you to call the function at a set interval.

If you would like to limit how many times a function can be called regardless of the space between the function calls, you can use the following method.

Define a factory function to hold the current time, count and queue then return a function which checks the current time against the last recorded current time and the count then either executes the first item in the queue, or waits until the next second to try again.

Pass a callback function to the function created by the factory function. The callback function will be entered into a queue. The limit function executes the first 10 functions in the queue and then waits until this interval has finished to execute the next 10 functions until the queue is empty.

Return the limit function from the factory function.

var factory = function(){
    var time = 0, count = 0, difference = 0, queue = [];
    return function limit(func){
        if(func) queue.push(func);
        difference = 1000 - (window.performance.now() - time);
        if(difference <= 0) {
            time = window.performance.now();
            count = 0;
        }
        if(++count <= 10) (queue.shift())();
        else setTimeout(limit, difference);
    };
};

var limited = factory();
var alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ".split("");

// This is to show a separator when waiting.
var prevDate = window.performance.now(), difference;

// This ends up as 2600 function calls, 
// all executed in the order in which they were queued.
for(var i = 0; i < 100; ++i) {
    alphabet.forEach(function(letter) {
        limited(function(){
            /** This is to show a separator when waiting. **/
            difference = window.performance.now() - prevDate;
            prevDate   = window.performance.now();
            if(difference > 100) console.log('wait');
            /***********************************************/
            console.log(letter);
        });
    });
}


You have to do it a little different:

var alphabet = ["A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "X", "Y", "Z"];

function printLetter(letterId) {
    if (letterId < alphabet.length) { // avoid index out of bounds

        console.log(alphabet[letterId]);

        var nextId = letterId + 1
        if (nextId < alphabet.length) // if there is a next letter print it in 10 seconds
            setTimeout("printLetter(" + nextId + ")", 10000/*milliseconds*/);
    }
}

printLetter(0); // start at the first letter

Demo: 

var alphabet = ["A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "X", "Y", "Z"];

function printLetter(letterId) {
  if (letterId < alphabet.length) { // avoid index out of bounds

    console.log(alphabet[letterId]);
    document.body.innerHTML += "<br />" + alphabet[letterId]; // for ***DEMO*** only

    var nextId = letterId + 1
    if (nextId < alphabet.length) // if there is a next letter print it in 10 seconds
      setTimeout("printLetter(" + nextId + ")", 100 /*milliseconds*/ ); // one second for ***DEMO*** only
  }
}

printLetter(0); // start at the first letter

Tags:

Javascript

Rate Limiting

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