Uncaught TypeError: Cannot read property 'getElementsByTagName' of null

StackOverflow https://stackoverflow.com/questions/23264313

  •  08-07-2023
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Question

I'm trying to select elements with .getElementsByTagName(). 

var tags = document.body.getElementsByTagName("*");

Current attempt using lessons learned from an existing answer https://stackoverflow.com/questions/7410949/javascript-document-getelementsbyclassname-compatibility-with-ie/7410966#7410966

But my attempt failed and I have this error:

Uncaught TypeError: Cannot read property 'getElementsByTagName' of null

Why is it producing this error and how can I fix it?

Était-ce utile?

La solution

Move the <script> from the <head> element to the <body> element.


document.body won't get a value assigned to it until the body element has been created.

Since you are trying to get all the elements in the <body>, you'd want to be at the end of the body element. Or put it in a function and call it from an event that fires after the body has been created (such as the window load event). To read more about that try, https://developer.mozilla.org/en-US/docs/Web/API/Window/load_event.

Autres conseils

Function examples:

Example with both methods:

function init() {
  alert("hello javascript");
};

window.addEventListener("load",init,false);

$(document).ready(function () {
  alert("hello jQuery");
});

http://jsfiddle.net/Ln5zu4Lt/

Be careful, the JavaScript example above waits for page load (images, iframes, etc.). This takes more time than jQuery's ready.

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