javascript - Using setInterval with $(document).ready

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javascript - Using setInterval with $(document).ready

posted Jan 31, 2022 in Technique[技术] by 深蓝 (71.8m points)

javascript - Using setInterval with $(document).ready

Am trying to invoke a function after the loading of the html page. Its working fine and I want the function to be invoked after every 3 seconds and hence inserted the setInterval() for it. But the function is not at all getting called. Is there any problem with the syntax of setInterval()..?

<html>
<head>

<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.11.0/jquery.min.js">
</script>

<script>
$(document).ready( setInterval(function(){f()},3000); );

function f()
{
xhttp=new XMLHttpRequest();
xhttp.open("GET","/anu/get.php",true);
xhttp.send();
xhttp.onreadystatechange = function(){

if(xhttp.readyState==4){
var Display = document.getElementById('new');
Display.innerHTML = xhttp.responseText;
}

}

}

</script>
</head>
<body>

<p id="new"> </p>

<body>

</html>

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1 Reply

深蓝 · Answer 1 · 2022-01-31T07:05:58+0000

It should be:

$(document).ready(function () {
  setInterval(function(){f()},3000);
});

The problem here is that setInterval returns a number, and passing a number to $(document).ready(...) does nothing. Instead, you need to pass $(document).ready(...) a function, such as a function that starts off the setInterval call.

The other problem is that you included a semicolon after the setInterval, but semicolons are only valid on statements (which you can think of as "things that stand on their own line"). You can only pass expressions to functions like setInterval, and expressions don't have semicolons, so your extra semicolon before the closing parenthesis is an error, because the JS engine sees a semicolon-terminated statement where it expects there to be a no-semicolon expression.

Also, you can shorten this to just

$(document).ready(function () {
  setInterval(f, 3000);
});

or even

$(function () {
  setInterval(f, 3000);
});

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javascript - Using setInterval with $(document).ready

javascript - Using setInterval with $(document).ready

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