API References

general

You can see list of options and sub commands with --help option.

$ jqf -h
Usage: jqf [method] [options] "<JavaScript function>"

Process stdin JSON string with JavaScript function.

Options:
  -V, --version            output the version number
  -r, --raw-string-output  no quotations with string output
  -m, --minify             minify output JSON
  -h, --help               output usage information

Examples:
  $ jqf             'obj => obj.value'
  $ jqf map         'arr => arr.id'
  $ jqf find        'arr => arr.id === 1'
  $ jqf filter      'arr => !arr'
  $ jqf some        'arr => arr % 2 === 0'
  $ jqf every       'arr => arr % 2 === 0'
  $ jqf reduce      '(prev, item) => /* reduce */' '"value"'
  $ jqf reduceRight '(prev, item) => /* reduce */' '"value"'
  $ jqf flatMap     'arr => arr'
  $ jqf keys
  $ jqf values
  $ jqf entries
  $ jqf fromEntries
  $ jqf flat

basic Usage

process single JSON input

$ command | jqf [options] <JavaScript function>

  • command should be executable and its output should be valid JSON string

  • <JavaScript function> should be valid JavaScript function, which takes an object parsed from the given JSON string via stdin, processes and returns its result to stdout

  • Result will be a stringified JSON described below

    • {"key": "value"}
    • [1,2,3]
    • true
    • 0
    • "string"
    • etc.

  • You can pass some [options] described below

    optionsabbr.descriptions
    --raw-string-output-rstrip quotation "" from string result
    --minify-mminify output JSON string

examples

process object
$ echo '{"hello":"world"}' | jqf 'obj => obj.hello'
"world"
most simple projection
$ echo '{"hello":"world"}' | jqf
{
  "hello": "world"
}
strip quotation from string result
$ echo '{"hello":"world"}' | jqf --raw-string-output 'obj => obj.hello'
world
array map
$ echo '[1,2,3]' | jqf 'nums => nums.map(n => n * 2)'
[
  2,
  4,
  6
]
minify option
$ echo '[1,2,3]' | jqf --minify 'nums => nums.map(n => n * 2)'
[2,4,6]

Array shorthands

We provide shorthand notations for some of Array.prototype methods with subcommand.

$ command | jqf [method] [options] <JavaScript function>

methods with examples

Array.prototype.find
# find the first even number.
$ echo '[1,2,3]' | jqf find 'n => n % 2 === 0'
2
Array.prototype.every
# check if all the number is under 10.
$ echo '[1,2,5,7,9]' | jqf every 'n => n < 10'
true
Array.prototype.some
# check if some even numbers are included.
$ echo '[1,3,5,7,9]' | jqf some 'n => n % 2 === 0'
false
Array.prototype.map
# calculate cubic values for all the elements
$ echo '[1,2,3]' | jqf map --minify 'n => Math.pow(n, 3)'
[1,8,27]
Array.prototype.flatMap
# flatten and calculate cubic values for all the elements
$ echo '[[1],2,3]' | jqf flatMap --minify 'n => Math.pow(n, 3)'
[1,8,27]
Array.prototype.filter
# pick even numbers
$ echo '[1,2,3,5,7,8,10]' | jqf filter --minify 'n => n % 2 === 0'
[2,8,10]
Array.prototype.reduce

You can provide reduce initial value as 2nd argument, which should be valid JSON string. Be careful that string values require quotations "", i.e. '"string value"'.

# calculate sum
$ echo '[1,2,3,4,5,6,7,8,9,10]' | jqf reduce '(prev, n) => prev + n' '0'

# concatenate strings
$ echo '["a", "b", "c"]' | jqf reduce '(prev, str) => prev + str' '"word: "'
"word: abc"
Array.prototype.reduceRight
# concatenate strings in reverse
$ echo '["a", "b", "c"]' | jqf reduceRight '(prev, str) => prev + str' '"word: "'
"word: cba"
Object.keys
# get keys of given object
$ echo '{"a":1, "b":2, "c":3}' | jqf keys -m
["a","b","c"]
Object.values
# get values of given object
$ echo '{"a":1, "b":2, "c":3}' | jqf values -m
[1,2,3]
Object.entries
$ echo '{"a":1, "b":2, "c":3}' | jqf entries -m
[["a",1],["b",2],["c",3]]
Object.fromEntries
$ echo '[["a",1],["b",2],["c",3]]' | jqf fromEntries -m
{"a":1, "b":2, "c":3}
Array.flat
$ echo '[["a",1],["b",2],["c",3]]' | jqf flat -m
["a",1,"b",2,"c",3]

advanced Usage (β features)

multiple stream inputs

You can pass multiple stream inputs via stdin:

$ cat <(echo '{"val": 1}') <(echo '{"val": 2}') | jqf '(x, y) => x.val + y.val'
3
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