How to Open a File for Reading Using JavaScript

1). Right-click the HTML file you want to use to open the file and select "Open With." Click your preferred JavaScript or HTML editor in the list of programs.
2). Open the file. The following code opens the file and assigns the file handler to the "file" variable:

file = fopen("filename.txt", 0);

Replace "filename.txt" with the name of your file.
3). Read the file's content and assign the content to a string variable, in this case, the "content" variable:

length = flength(file);
content = fread(file, length);
4). Close the file. After you finish reading the file content, you must close the handler.

fclose(file);