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how do i call a function to count the number of divs with an id of 'd1' after the page loads. right now i have it in my section but doesnt that execute the script before anything in the loads? because it works if i put the code below the div tags...

how do i call a function to count the number of divs with an id of 'd1' after the page loads. right now i have it in my section but doesnt that execute the script before anything in the loads? because it works if i put the code below the div tags...

  • javascript
  • function
  • call
Share Improve this question asked Feb 13, 2010 at 0:46 DavidDavid 2,4238 gold badges38 silver badges59 bronze badges 0
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4 Answers 4

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Firstly there should be at most one because IDs aren't meant to be repeated.

Second, in straight Javascript you can call getElementById() to verify it exists or getElementsByTagName() to loop through all the divs and count the number that match your criteria.

var elem = document.getElementById("d1");
if (elem) {
  // it exists
}

or

var divs = document.getElementsByTagName("div");
var count = 0;
for (var i = 0; i < divs.length; i++) { 
  var div = divs[i];
  if (div.id == "d1") {
    count++;
  }
}

But I can't guarantee the correct behaviour of this because like I said, IDs are meant to be unique and when they're not behaviour is undefined.

Use jQuery's document.ready() or hook up to the onLoad event.

well an ID should be unique so the answer should be one.

you can use <body onload='myFunc()'> to call a script once the DOM is loaded.

You need to have the function tied to the onload event, like so:

window.onload = function() {
    var divElements = document.getElementById("d1");
    var divCount = divElements.length;
    alert(divCount);
};

For the record, you should only have one div with that ID, as having more than one is invalid and may cause problems.

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