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The setInterval() method in JavaScript and make your own Interval Function

davidbell_space profile image David Bell Originally published at davidbell.space Updated on ・1 min read

setInterval() is a window method available to us. It takes two things:

  • A callback function
  • Time in milliseconds
setInterval(() => {
console.log('Hoopla')
}, 1000)
// Hoopla
// Hoopla…
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In the example an anonymous function () => is passed in. The time in milliseconds is passed at the very end }, 1000). Hoopla is printed to the console after 1 second has passed once rendered and again every second after.

You can also pass a function into setInterval.

const oneSec = () => {
console.log('Hoopla')
}
// Hoopla
// Hoopla…

setInterval(oneSec, 1000)
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The function oneSec() is ran after 1000 milliseconds then again every 1000 milliseconds.

A nuisance with setInterval() however is that is doesn’t run the function for the first time until the time passed in has passed.

For example the function below will wait 5 seconds before ‘Hoopla’ is first printed to the console. And then continue to run every 5 seconds after.

setInterval(() => {
console.log('Hoopla')

}, 5000)
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You can however create your own interval function that will begin immediately.

Make your own

const hoopla = () => console.log("Hoopla")

const myInterval = (func, time) => {
  func()
  return setInterval(hoopla, time)
}
myInterval(hoopla, 2000)
// Hoopla
// Hoopla…
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This functions takes a function as a parameter as well a time function, time. The function is immediately called and we return a regular setInterval. This is great because it works immediately with no day unlike a regular setInterval.

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