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Is it true that there are no guarantees across major browsers that the following script tags will always execute both sequentially AND in order of declaration? i.e. should I assume that the following code will not always yield x == 'ab' in alert?
<head> <script type="text/javascript"> //tag A var x = x || ''; x += 'a'; </script> <script type="text/javascript"> //tag B var x = x || ''; x += 'b'; </script> </head> <body> <script type="text/javascript"> alert('x='+x); <script> </body> ... and it's possible that x will instead be one of the following:
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It doesn't matter whether it's an external script or an inline script - they are executed in the order they are encountered in the page. Inline scripts that come after external scripts are held until all external scripts that came before them have loaded and run.
No, you should always load Javascript in the order that it's needed. If you're using some jQuery plugins, then you should load jQuery before those plugins, as they may instantiate something that uses the jQuery object(s) without you knowing.
Script tags are executed in the order they appear It also means scripts which appear later on the page can depend on things scripts which appear earlier have done. Elements on the page won't render until all the script tags preceding them have loaded and executed.
The browser loads the html (DOM) at first. The browser starts to load the external resources from top to bottom, line by line.
The execution order of these non-dynamically added script tags should be purely sequentially in every browser:
Snippet from this link:
JavaScript statements that appear between
<script>and</script>tags are executed in order of appearance; when more than one script appears in a file, the scripts are executed in the order in which they appear.
However, things could change as soon as you're:
defer attribute.
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