Convert JSON string to Key / Value Arrays

Question

Convert JSON (key/value pairs) to two native arrays, one array of keys and another of values, in your language.

var X = '{"a":"a","b":"b","c":"c","d":"d","e":"e","f":"f9","g":"g2","h":"h1"}';

The value array could be an array of strings or integers.

So we need two functions keys & vals, returning native arrays on input of JSON string.

In above example the output would be:

keys : ["a", "b", "c", "d", "e", "f", "g", "h"]
vals : ["a", "b", "c", "d", "e", "f9", "g2", "h1"]

Here is my attempt at this using javascript:

keys : (53 Chars)

function keys(X){return X.match(/[a-z0-9]+(?=":)/gi)}

vals : (56 Chars)

function vals(X){return X.match(/[a-z0-9]+(?="[,}])/gi)}

Can other languages challenge this??

Answer 1

Python, 27/30

To actually comply with the rules:

keys=lambda x:list(eval(x))
vals=lambda x:eval(x).values()

Python, 30

Just using one function:

lambda x:zip(*eval(x).items())

This will separate the keys from the values and return them in a list.

Python, 7

If returning a dictionary is allowed, then this is all you need:

eval(x)

Answer 2

APL 32

Index origin 1. If you will accept the keys and values being returned as a two row array then a simple one liner will do the job in APL. This takes screen input via ←⍞

⍉((.5×⍴j),2)⍴j←(~j∊'{":;,}')⊂j←⍞

Taking the given example as input:

{"a":"a","b":"b","c":"c","d":"d","e":"e","f":"f9","g":"g2","h":"h1"};

a b c d e f  g  h
a b c d e f9 g2 h1

Answer 3

Perl 28 bytes

Instead of 2 separate functions to return keys and values, I'm returning both in the form of a hash.

sub j2h{eval pop=~y/:"/,/dr}

Sample usage:

$_='{"a":"a","b":"b","c":"c","d":"d","e":"e","f":"f9","g":"g2","h":"h1"}';
%h=j2h($_);
print $h{f}; # prints f9
print $h{g}; # prints g2

It even works for arbitrarily deeply nested variables:

$_='{"a":{"b":{"c":"c3","d":"d4"},"c":"c5"},"b":"b6"}';
%h=j2h($_);
print $h{a}{b}{d}; # prints d4
print $h{a}{c};    # prints c5

Answer 4

Tcl 69,69

first attempt 132 keys+vals

proc j {x n} {
regsub -all {(".*?"):(".*?")} $x "\[lappend o \\$n\]" x
subst $x
set o $o
}
proc keys x {j $x 1}
proc vals x {j $x 2}

second try 69 keys, 69 values

proc keys x {regsub -all {(".*?"):(".*?").} $x {\1 } x
lindex $x\} 0}

proc vals x {regsub -all {(".*?"):(".*?").} $x {\2 } x
lindex $x\} 0}

Answer 5

K, 22

{+`$":"\:'","\:1_-1_x}

The double quotes in the input string have to be escaped

k){+`$":"\:'","\:1_-1_x} "{\"a\":\"a\",\"b\":\"b\",\"c\":\"c\",\"d\":\"d\",\"e\":\"e\",\"f\":\"f9\",\"g\":\"g2\",\"h\":\"h1\"}"
"a" "b" "c" "d" "e" "f"  "g"  "h"
"a" "b" "c" "d" "e" "f9" "g2" "h1"

For the same bytecount you could just read from stdin

+`$":"\:'","\:1_-1_0:0

.

k)+`$":"\:'","\:1_-1_0:0
{"a":"a","b":"b","c":"c","d":"d","e":"e","f":"f9","g":"g2","h":"h1"}
"a" "b" "c" "d" "e" "f"  "g"  "h"
"a" "b" "c" "d" "e" "f9" "g2" "h1"

Answer 6

PHP, 56/58

Pssh, PHP has functions for this stuff (although it won't win the shortest answer award).

function keys($j){return array_keys(json_decode($j,1));}
function vals($j){return array_values(json_decode($j,1));}

Answer 7

APL (Dyalog Unicode), 18 bytes^SBCS

Anonymous tacit prefix function. Prints list of keys, then returns list of values.

'⍎¨⎕←⎕NL¯2'⍎⍨⎕JSON

Try it online!

⎕JSON convert JSON string to APL namespace object

'…'⍎⍨ in that namespace, execute the following code:

 ⎕NL¯2 name list for all all variables

 ⎕← print that list

 ⍎¨ execute each name

Answer 8

PowerShell, 34/36 28/28 bytes

-14 bytes total thanks to @mazzy!

To fetch the keys:

&(gcm *F*son)"$args" -a|% k*

Try it online!

To fetch the values:

&(gcm *F*son)"$args" -a|% v*

Try it online!

Kinda cheap, as it uses the built-in method ConvertFrom-Json -AsHashtable to convert the data from JSON.

Answer 9

ECMAScript

I'm surprised no one has proposed a better ECMAScript solution, so here's my simple attempt:

keys: (29 chars)

X=>Object.keys(JSON.parse(X))

values: (31 chars)

X=>Object.values(JSON.parse(X))

Answer 10

jq, 11–∞ bytes

Try it online!

This answer will take some refining, as I'm not yet clear on the rules. It states that two functions are required, but jq doesn't have functions and I don't know how much of our current meta consensus applies to such old posts

The essence is in two snippets:

• keys: keys
• values: [.[]]

These are both valid jq programs that each give their respective piece. Counted like this we have 11 bytes. We can also do:

# Return an array of arrays as [keys, values]
[keys, [.[]]]

# Return another nice JSON as {"keys": keys, "values": values}
{keys:keys, values:[.[]]}

I'll add a bit more explanation when the final entry is clearer.

Answer 11

C (gcc), 103 bytes

char*b[99],**o,*l;f(s,n)char*s;{for(o=b;*s++;l=*s-34?l:++n%4?s+1:(*o++=strndup(l,s-l)));*o=0;return b;}

Try it online!

Usage:

f(input, 2) returns an array with the keys

f(input, 0) returns an array with the values

C (clang), 67 bytes

*l;f(*s,n){for(;*s++;l=*s-34?l:++n%4?s+1:printf("%.*ls\n",s-l,l));}

Writes the output to stdout instead of returning arrays.

Try it online!

Answer 12

Ruby, 19

eval X.gsub':','=>'

Similar, unsurprisingly, to the Perl solution. The Ruby 1.9 literal for a Hash would be identical to the input form if it weren't for the quoted keys; as it is we just need to convert the colons to =>.

Answer 13

CoffeeScript:

vals = []
keys = []
vals.push(v) and keys.push(k) for own k, v of JSON.parse(X)

Answer 14

Lua

function keys(x)return loadstring("return"..x:gsub(':".-"',''))()end
function vals(x)return loadstring("return"..x:gsub('"[^"]*":',''))()end

68 and 71 chars

Answer 15

Tcl 8.6, 82

 package r json;lmap keys [dict k [set d [json::json2dict $X]]] vals [dict v $d] {}

The Tcl core is (unlike php) very small.
This requires the tcllib, which is available as package for most linux distributions.
I use this library because too much languages have a json_parse build in.

Answer 16

PHP 7.4+, 39/41 bytes

(demo)

The keys via closure with PHP7.4 arrow function syntax: 39 bytes

(fn()=>array_keys(json_decode($X,1)))()

The values via closure with PHP7.4 arrow function syntax: 41 bytes

(fn()=>array_values(json_decode($X,1)))()

Answer 17

Python 3 (Total 35 characters)

Input JSON String

X = '{"a":"a","b":"b","c":"c","d":"d","e":"e","f":"f9","g":"g2","h":"h1"}'

Get Keys(16 characters)

k=eval(X).keys()

Get Values(18 characters)

v=eval(X).values()

Try online

Answer 18

Burlesque, 12 bytes

'";;:an2cou[

Try it online!

'";; # Split by "s
:an  # Filter by alphanumeric
2co  # Group in pairs
u[   # Unzip giving array of vals and array of keys