Recently whilst working on my Aurelia 2 book, for the example application where you checkout I needed to add in the ability to provide a card number and when it saves, the last 4 digits of the card number get saved.
This is one of those things that as developers we won’t do too often, but it’s easy using
substr to trim a text string to a certain length.
let ccNumber = '4560265043620583'; let lastFourDigits = ccNumber.substr(-4);
-4 as the value to
substr you’re telling it to take the last 4 characters from the string. The result from our example will be
0583. You can also provide non-negative numbers to go from the beginning as well.
I am sure there are other ways of doing the same thing, but I always look for the easiest to read and easiest to understand solutions and
substr fits the bill nicely.