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From: Ben Bacarisse <ben.usenet@bsb.me.uk>
Newsgroups: comp.lang.javascript
Subject: Re: Filter array of objects for property
Date: Thu, 13 Oct 2016 00:27:03 +0100
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Andrew Poulos <ap_prog@hotmail.com> writes:

> If I have an array that looks like this
>
> var arr =
> [
>   {
>     a: "foo_2",
>     b: "trigger_1",
>     c: "bar_3"
>   },
>   {
>     a: "foo_3",
>     b: "foo_4",
>     c: "bar_4"
>   },
>   {
>     a: "foo_6",
>     b: "trigger_5",
>     c: "bar_5"
>   }
> ...
> ];
>
> and to get an array of all "b" values that start with "trigger_" and
> end with a number I'm calling
>
> function getValues(theArr, pre) {
>   var i = 0,
>       fnd = [],
>       tmp;
>
>   for (i = 0; i < theArr.length; i++) {
>     tmp = theArr[i].b;
>     if ( /trigger_\d+$/.test(tmp) ) {
>       fnd.push(tmp);
>     }
>   }
>
>   return fnd;
> }
>
> While this works I'd like the argument "pre" to be a string I pass to
> the regexp so that I can test other values and not just "trigger_" but
> I don't know how.

You can construct a RegExp from a string:

  RegExp(pre + '\\d+$').test(tmp)

> And secondly is there an easier way to get values for an array of
> objects?

One way would be to use map and filter.  Combining these with the arrow
notation for functions you could write:

  arr.map(x => x.b).filter(x => RegExp(pre + '\\d+$').test(x))

(ES6 would also permit you to write `${pre}\\d+$`)

-- 
Ben.