external script usage in javascript

Can i开发者_JS百科 use external script only with .js extensions? Can't i use it when using the extension as .htm?

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You can. What matters is the MIME type with which the script is served (by the server). It should be

application/javascript

or

application/x-javascript

This is used by certain PHP scripts that have the .php extension, but actually serve JavaScript (not that I like this, but it's possible).

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Theoretically the extension is not important, it´s the MIME type the server serves the resource that´s important.

In practice there has existed issues with UAs from vendors (IE) that has been file extension maniacs.

Another issue is if you serve the page from the file-protocol.

So my advice, stick with .js

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Most jsonp is done with an external php file. Even YQL doesn't use the js extension. So yes you are able to and in fact most people do.