Support array notation in property path

[leesei]

The doc said it is supported but actually not.
It is not covered in test.

const get = require('get-value');
const obj = { e: [ {f : 'g'} ] };
console.log(get(obj, 'e[0].f')); // undefined
console.log(get(obj, 'e.0.f')); // 'g'

[jonschlinkert]

I pushed up a branch with support for array-notation, but I haven't made up my mind on whether or not to support it, since it has a slight impact on performance.

how were you thinking of using this feature? what use case? It might help me decide. thanks!

[leesei]

I'm converting these to JSON in leesei/openslide-prop2json.

openslide.level[0].downsample: '1'
openslide.level[0].height: '32893'
openslide.level[0].tile-height: '240'
openslide.level[0].tile-width: '240'
openslide.level[0].width: '46000'
openslide.level[1].downsample: '4.0000608050589808'
openslide.level[1].height: '8223'
openslide.level[1].tile-height: '240'
openslide.level[1].tile-width: '240'
openslide.level[1].width: '11500'
openslide.level[2].downsample: '16.003163017031632'
openslide.level[2].height: '2055'
openslide.level[2].tile-height: '240'
openslide.level[2].tile-width: '240'
openslide.level[2].width: '2875'

My current implementation also does not convert them to array.

Also, we must use array notation for hyphenated keys: object['foo-bar']: 3.

Did you have the performance test set up?

I would like to try this:
var segs = prop.split(/[.\[\]]/).filter(function (s) { return s; });

[jonschlinkert]

Did you have the performance test set up?

yes, if you git clone then do npm install -D, then run node benchmark, you can see how changes effect the speed.

however... the regex you mentioned won't work since ]. is two characters. You'll need to add + after the last bracket, like: /[.\[\]]+/.

see https://github.com/jonschlinkert/get-value/blob/array-notation/index.js#L26

[leesei]

I'm guessing that the or(|) in your regex causes backtracking.
I'm splitting ] and . (excessively) so I have to filter the empty segment.
I can try different regex and compare the performance. Thanks for the great work.
I'll get back to you.

[jonschlinkert]

no worries, thanks

[leesei]

http://jsperf.com/get-value-array-notation

Alas, I'm ashamed to put the "split and filter" code up, it only have 23000 ops.
Feel free to edit the test.

[leesei]

The performance was decreased with this added feature by more than 50%. I also hesitate to merge it to master.

I suggest adding an option for this use case.

var get = require('get-value')({arrayNotation: true});

index.js would export closure that set a SPLIT_SEPERATOR variable and return the current implementation with this modification:
var segs = prop.split(SPLIT_SEPERATOR);

[leesei]

Or we can allow user to pass the separator to support more use cases.

var GetValue = require('get-value');
var get1 = GetValue({separator: GetValue.DOT_ONLY}); // default
var get2 = GetValue({separator: GetValue.SUPPORT_ARRAY_NOTATION});
var get3 = GetValue({separator: '_'}); // custom separator

[jonschlinkert]

suggest adding an option for this use case.

Hmm, maybe we can take a function as the third argument, which would be expected to return an array of property paths.

thoughts?

[leesei]

That's great.
It provides the same feature without having to export a constructor function.

const get = require('get-value');
const obj = { e: [ {f : 'g'} ] };
// default tokenizer using '.'
// trying to access `obj['e[0]']`
console.log(get(obj, 'e[0].f')); // undefined
// custom tokenizer
// take cares of array notation
console.log(get(obj, 'e[0].f', (prop) => prop.split(/(?:\.|\[|\]\.)/)); // 'g'

[leesei]

Tangential to this issue
I suggest a, b, c to be removed, see #5

[leesei]

Now that the a, b, c params are kept, how should the function be added?

One way is to switch between the two features:

if (typeof a === 'function') {
  tokenizer = a;
} else {
  // allowing for multiple properties to be passed as
  // a string or array, but much faster (3-4x) than doing
  // `[].slice.call(arguments)`
  if (a) prop += '.' + toString(a);
  if (b) prop += '.' + toString(b);
  if (c) prop += '.' + toString(c);
}

[jonschlinkert]

Closing since this was implemented a while ago.

[crysislinux]

@jonschlinkert Could you please give an example? I tried split and separator options but cannot make it work. Thanks.

[doowb]

The README.md has an example for how to use the split option. If that doesn't work, please open an issue with an example of the code your are trying.