Creating And Displaying Summaries Of Text?

What I want to do is on the blog's main html page is to have the whole story printed. On other html pages, I want only the first 100 characters of the story to be printed, as a summary of the story. One way would be to manually count the 100 characters, copy the text, and paste it into all the html pages I want the summary to show. (Too much work). Or I figured I could use script to do it for me. Would Javascript be the best way to do this? Would I store the blog text in an external .js file and assign a variable to it (such as var x="blog story text") and call upon the variable to display the full text on the blog story html page? And then in the external .js file, run a procedure that counts the first 100 characters and stores it in another variable, then call upon this other variable in the .html files where the summary is printed? If so, since there would be many blog stories, would I create an external .js file for each blog story, since the javascrpt file would become to big and slow down loading time?