CODEWITHSUNDEEP
javascriptdom-events
Doug Null
Doug Null

Reputation: 8327

Does a JavaScript setTimeout function stop when page reloaded?

If I initiate a setTimeout function from the <body onload...> trigger, will the function stop when the page is reloaded?

I initiate a setTimeout function periodic_update() on the onload event of my page.

Is this creating multiple instances of the periodic_update() function process?

<body onload="init_page_onload()">
    
function init_page_onload() {
    periodic_update();      
}

function periodic_update() {  
        foo()

    setTimeout("periodic_update()", PERIODIC_UPDATE_REPEAT_PERIOD_MS )
}

Upvotes: 7

Views: 6135

Answers (3)

pfries
pfries

Reputation: 1758

When you reload the browser, the html, css and javascript are re-evaluated as part of building the DOM and render trees. Consequently, each instance of the timer function is disposed on page reload. So, no, you will not end up with multiple instances of that function.

Upvotes: 1

pimvdb
pimvdb

Reputation: 154918

In the browser, all JavaScript code is aborted when you leave the page, and run when you open the page. So timeouts will be cleared and set again when you reload a page.

If you want to persist a timeout, you could:

  • use a parent frame which doesn't reload
  • use localStorage (which allows you to persist data on the client's computer) to keep track of when the function was last called, and set the timeout appropriately on load

Upvotes: 4

Adriano Repetti
Adriano Repetti

Reputation: 67128

When page is reloaded the "previous" timer is discarded and a new one will start.

Upvotes: 9

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