I have this setinterval with function alert:
setInterval(function(){
alert('oo');
}, 5000);
But I would like to change my (5000) interval each time interval runs alert() - I'd like have it randomly selected between 5 - 10 seconds. How can I do it?
You should use setTimeout to set interval after which the function should be executed.
function myFunction() {
var min = 5,
max = 10;
var rand = Math.floor(Math.random() * (max - min + 1) + min); //Generate Random number between 5 - 10
console.log('Wait for ' + rand + ' seconds');
setTimeout(myFunction, rand * 1000);
}
myFunction()
You can do it like this:
function myFunction() {
alert('oo');
setTimeout(myFunction, Math.random() * 5000)
}
myFunction()
You can do this with two methods, first setTimeout and second requestAnimationFrame.
Here are the full examples of both.
Random interval with setTimeout
function randomInterval(callback, min, max) {
let timeout;
const randomNum = (max, min = 0) => Math.random() * (max - min) + min;
const stop = () => clearTimeout(timeout)
const tick = () => {
let time = randomNum(min, max);
stop();
timeout = setTimeout(() => {
tick();
callback && typeof callback === "function" && callback(stop);
}, time)
}
tick();
}
Random interval using requestAnimationFrame
function randomInterval(callback, min, max) {
const randomNum = (max, min = 0) => Math.random() * (max - min) + min;
let targetTime = randomNum(min, max);
let lastInvoke = performance.now();
const stop = () => targetTime = null
const tick = () => {
if (!targetTime) return;
if (performance.now() - lastInvoke > targetTime) {
lastInvoke = performance.now();
targetTime = randomNum(min, max);
callback && typeof callback === "function" && callback(stop);
}
requestAnimationFrame(tick)
}
tick();
}
and here is an example of how to call it
randomInterval((stop) => {
// do what you want...
if (stopCondition) {
stop();
}
}, 1000, 3000)
Intervals, once set, are fixed.
Use setTimeout and call the function recursively instead.
function myAlert() {
setTimeout(myAlert, generate_random_time());
alert('oo');
}
The only potential issue with most of the current answers here is that the initial function call does not have the random delay, only the subsequent calls.
A modification is to place the function outside the loop then call it inside the setTimeout:
function doSomething() {
console.log("Hello");
}
(function loop() {
var rand = Math.round(Math.random() * 10);
setTimeout(function() {
doSomething();
console.log("Delayed " + rand + " secs.");
loop();
}, rand*1000);
}());
Learning ES6 converting to arrow functions and template literals the code looks like:
function doSomething() {
console.log("Hello");
}
(function loop() {
let rand = Math.round(Math.random() * 10);
setTimeout( () => {
doSomething();
console.log(`Delayed ${rand} secs`);
loop();
}, rand*1000);
}());
Adapted from a very similar thread:https://stackoverflow.com/questions/6962658/randomize-setinterval-how-to-rewrite-same-random-after-random-interval
setInterval, but set a new timeout instead after each alert.