Create function padLeft with keyup

I'm trying to create a function where the user reports a 6-digit number + the year

For example:

• If I type: 12016 = > 000001/2016
• If I type: 122016 = > 000012/2016
• If I type: 1232016 = > 000123/2016
• If I type: 12342016 = > 001234/2016

And then I have to put a slash before the last 4 numbers to consider as Year .

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