Run Function only once in Javascript [duplicate]

Question

Execute function only one time in Javascript, no matter how many times it has been called. I write the following code, but does not working.

var counter = 0;

if(n.data === YT.PlayerState.BUFFERING) {
  setTimeout(function() {                 
    if(counter===0) {
      r.frontPlayer.seekTo(10);
      counter++;
  }}, 2000);
}

For that specific function, you don't even need the counter. setTimeout will only run it once. If you're running this whole block of code multiple times, then that's a different problem. — Mike Cluck
– Mike Cluck, Commented May 11, 2016 at 21:39
It looks like var counter = 0; is in the same scope where setTimeout is declared — Washington Guedes
– Washington Guedes, Commented May 11, 2016 at 21:40
which function are you talking about? setTimeout callback function or r.frontPlayer.seekTo(10) ? setTimeout callback function will run only once unless the whole code block you wrote executes again. — Saad
– Saad, Commented May 11, 2016 at 21:43
if(n.data === YT.PlayerState.BUFFERING) { r.frontPlayer.seekTo(10); } — busterscruggz
– busterscruggz, Commented May 11, 2016 at 21:44

Blue · Accepted Answer · 2016-05-11 21:43:21Z

3

Try not to use timeouts, they invite misery and suffering. This is a simple example, I use jquery for attaching the events but the function is independent of jquery. The key thing is using the object, the anonymous function in this case, to track state.

<button id="testButton">
test
</button>

$("#testButton").click(function() {
    if (null == this.ran) {
    console.log("do something");
    this.ran = true;
  }
})

answered May 11, 2016 at 21:43

Blue

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Comments

Andreas Louv · Accepted Answer · 2016-05-11 21:41:30Z

1

Take a look at underscore or lodash's _.once function:

var fn = _.once(function() {
  console.log('this will only run once');
});

Or writing it yourself:

var fn = (function() {
  var called = false;
  var ret;

  return function() {
    if (called) return ret;
    called = true;
    // do stuff
    // .. 
    ret = 'some return value';
    return ret;
  };
})();

edited May 11, 2016 at 21:41

answered May 11, 2016 at 21:39

Andreas Louv

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2 Comments

Mikey Over a year ago

Really? You want him to use a library just for this...?

Andreas Louv Over a year ago

@Mikey Accidentally pressed submit before posting a "polyfill"

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