Should I write script in the body or the head of the html

Question

I have seen both ways  both implementation work just the structures are a bit different  In your experience  which work better and why

User · Accepted Answer

I would answer this with multiple options actually, the some of which actually render in the body.

Place library script such as the jQuery library in the head section.
Place normal script in the head unless it becomes a performance/page load issue.
Place script associated with includes, within and at the end of that include. One example of this is .ascx user controls in asp.net pages - place the script at the end of that markup.
Place script that impacts the render of the page at the end of the body (before the body closure).
do NOT place script in the markup such as <input onclick="myfunction()"/> - better to put it in event handlers in your script body instead.
If you cannot decide, put it in the head until you have a reason not to such as page blocking issues.

Footnote: "When you need it and not prior" applies to the last item when page blocking (perceptual loading speed). The user's perception is their reality—if it is perceived to load faster, it does load faster (even though stuff might still be occurring in code).

EDIT: references:

asp.net discussion: http://west-wind.com/weblog/posts/154797.aspx and here: http://msdn.microsoft.com/en-us/library/3hc29e2a.aspx
jQuery document ready discussion: http://encosia.com/2010/08/18/dont-let-jquerys-document-ready-slow-you-down/?utm_source=feedburner&utm_medium=email&utm_campaign=Feed%3A+Encosia+%28Encosia%29
the other answers on this question present valid information as well.
use www.google.com and www.bing.com to search for related information (there are a lot of references)

Side note: IF you place script blocks within markup, it may effect layout in certain browsers by taking up space (ie7 and opera 9.2 are known to have this issue) so place them in a hidden div (use a css class like: .hide { display: none; visibility: hidden; } on the div)

Standards: Note that the standards allow placement of the script blocks virtually anywhere if that is in question: http://www.w3.org/TR/1999/REC-html401-19991224/sgml/dtd.html and http://www.w3.org/TR/xhtml11/xhtml11_dtd.html

EDIT2: Note that whenever possible (always?) you should put the actual Javascript in external files and reference those - this does not change the pertinent sequence validity.

User · Answer

The problem with writing scripts at the head of a page is blocking  The browser must stop processing the page until the script is download  parsed and executed  The reason for this is pretty clear  these scripts might insert more into the page changing the result of the rendering  they also may remove things that dont need to be rendered  etc    Some of the more modern browsers violate this rule by not blocking on the downloading the scripts  ie8 was the first  but overall the download isn t the majority of the time spent blocking   Check out Even Faster Websites  I just finished reading it and it goes over all of the fast ways to get scripts onto a page  Including putting scripts at the bottom of the page to allow rendering to complete  better UX

User · Answer

Head  or before closure of body tag  When DOM loads JS is then executed  that is exactly what jQuery document ready does

User · Answer

I always put my scripts in the header  My reasons    I like to separate code and  static  text I usually load my script from external sources The same script is used from several pages  so it feels like an include file  which also goes in the header

User · Answer

W3Schools have a nice article on this subject   Scripts in  lt head gt      Scripts to be executed when they are   called  or when an event is triggered    are placed in functions       Put your functions in the head   section  this way they are all in one   place  and they do not interfere with   page content    Scripts in  lt body gt      If you don t want your script to be   placed inside a function  or if your   script should write page content  it   should be placed in the body section

[javascript] Should I write script in the body or the head of the html?

Examples related to javascript

Examples related to html