create js file/code for other user to embed to use on their sites

I am creating a newsletter on my site, and after its completion I need to give a user a code to embed on their sites so they can directly show that pages on their sites. For this I am creating the HTML file f开发者_StackOverflow社区or the main newsletter pages, now the main problem for me is - how to create a JS script for it and give the code for embedding it to thier site.

Please give me some suggestions here

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You just echo the required code such that it will be displayed in a textbox in the site. Customize the embed code as required using php.