I was looking for something very simple that would copy spreadsheet rows to a document, all within Google Apps/Google Drive. There are plenty of mail merge and invoicing projects listed in the Google add-ons to accomplish some of this, but a lot of them require the use of third party sites or have more customization or features that I don't need. They are worth looking into though, as this requires some extra steps to use, like creating a developer API key.
You'll at least need a spreadsheet with data in it, and a document with template variables to fill in.
In order to use the Google Picker for a file dialog, you first need to get a Developer's API Key. After following the directions in the Google example, I was getting a lot of "invalid key" errors because I didn't wait long enough for it to be activated or sync'd with Google. Its not instantaneous.
I name the spreadsheet after the company I'm invoicing. That is used to fill in the Company Name on the template. The number of columns doesn't matter, but the code does assume the first row is a header row, and that there is at least a date column. Extra columns can exist, and if they don't match a template variable the data will just be skipped. My columns are:
Date, Description, Hours, Rate, Collected, Day Total
The document template will be cloned, so you can use it as many times as needed and across different spreadsheets. All template variables look like <<VariableName>>. Values can be replaced more than once, and there are several Global values available:
<<CompanyName>>: this is the spreadsheet's name unless defined otherwise in the code<<CurrentDate>>: today's date<<TotalDue>>: total dollar sum of all invoice rows added<<InvoiceNumber>>: today's date like '20160414'
Invoice item rows are in a table that must have a header and footer row. The header's first column must be called date because that's how its found by the code. See Main.gs::findInvoiceTable() function if you want to change it.
The code will copy the row with all the <<ItemXName>> values filled in. The XName in this case is the column name from your spreadsheet. Dates will be formatted and currency will be formatted.
You can add these scripts like any other Google script; by going to the spreadsheet and clicking Tools > Script Editor.... The name only matters for the HTML file, because that is referenced in the code. The rest can be named anything or combined.
You can edit the top of Main.gs if you want to change date or currency formats. You can also change the SpreadsheetName variable if you don't want to use it for the company name. Don't forget to fill out your API key in the Picker.html file.
You'll also have to setup a trigger for the menu item. In the script editor, I have Resources > All your triggers > On open > From spreadsheet. This just adds the "Invoicing" item in the menu bar:
