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    JavaScript object query engine

    STATUS: Jora is still very much work in progress. Syntax may change in next releases.


    • Tolerant to data stucture queries (e.g. just returns nothing for paths that not reachable)
    • Compact syntax for common tasks
    • Aggregate values across arrays and eliminate duplicates by default
    • Stat collecting mode (powers suggestions)
    • Tolerant parsing mode (useful to provide suggestions for query in an editor)
    • Extensible DSL on query build by custom method list

    Related projects:


    • [x] AST
    • [ ] Immutable paths hoisting (reduce computations -> performance)
    • [ ] Smart computation caching across queries
    • [ ] Query parts performance stat
    • [ ] Query transforming, e.g. query merge, subquery to a query, context inlining
    • [ ] Method namespaces, e.g. semver, path, math etc
    • [ ] Syntax highlighting
    • [ ] Prettifier
    • [x] Move jison to dev dependencies
    • [ ] Debugging (step by step evaluation)
    • [ ] Input data shape prediction suitable for a query (based on touching paths)

    More ideas and thoughts: Jora todo gist, Jora ToDo on Discovery.js projects state overview

    Table of content:


    Install with npm:

    npm install jora

    Basic usage:

    // ESM
    import jora from 'jora';
    // CommonJS
    const jora = require('jora');

    Bundles are available for use in a browser:

    • dist/jora.js – minified IIFE with jora as global
    <script src="node_modules/jora/dist/jora.js"></script>
      jora('query')(data, context);
    • dist/jora.esm.js – minified ES module
    <script type="module">
      import jora from 'node_modules/jora/dist/jora.esm.js'
      jora('query')(data, context);

    One of CDN services like unpkg or jsDelivr can be used. By default (for short path) a ESM version is exposing. For IIFE version a full path to a bundle should be specified:

    <!-- ESM -->
    <script type="module">
      import jora from '';
      import jora from '';
    <!-- IIFE with an export `jora` to global -->
    <script src=""></script>
    <script src=""></script>

    Quick demo

    Get npm dependency paths (as a tree) that have packages with more than one version:

    import jora from 'jora';
    import { exec } from 'child_process';
    function printTree() {
        // see implementation in examples/npm-ls.js
    exec('npm ls --all --json', (error, stdout) => {
        if (error) {
        const npmTree = JSON.parse(stdout);
        const depsPathsToMultipleVersionPackages = jora(`
            $normalizedDeps: => dependencies.entries().({ name: key, ...value });
                .group(=>name, =>version)
                .({ name: key, versions: value.sort() })
                .[versions.size() > 1];
            $pathToMultiVersionPackages: => .($name; {
                otherVersions: $multiVersionPackages[=>name=$name].versions - version,
                dependencies: $normalizedDeps()
                    .[name in $ or dependencies]

    Example of output:

    ├─ c8@7.11.0
    │  ├─ istanbul-lib-report@3.0.0
    │  │  └─ supports-color@7.2.0 [more versions: 8.1.1]
    │  ├─ test-exclude@6.0.0
    │  │  └─ minimatch@3.1.2 [more versions: 3.0.4]
    │  ├─ v8-to-istanbul@8.1.1
    │  │  └─ convert-source-map@1.8.0
    │  │     └─ safe-buffer@5.1.2 [more versions: 5.2.1]
    │  ├─ yargs-parser@20.2.9 [more versions: 20.2.4]
    │  └─ yargs@16.2.0
    │     └─ yargs-parser@20.2.9 [more versions: 20.2.4]
    ├─ eslint@8.10.0
    │  ├─ @eslint/eslintrc@1.2.0
    │  │  ├─ ignore@4.0.6 [more versions: 5.2.0]
    │  │  └─ minimatch@3.1.2 [more versions: 3.0.4]


    import jora from 'jora';
    // create a query
    const query = jora('');
    // or with custom methods
    const queryWithCustomMethods = jora.setup({
        myMethod(current) { /* do something and return a new value */ }
    // perform a query
    const result = query(data, context);
    const result = queryWithCustomMethods('foo.myMethod()')(data, context);


    • methods

      Type: Object
      Default: undefined

      Additional methods for using in query passed as an object, where a key is a method name and a value is a function to perform an action. It can override build-in methods.

    • debug

      Type: Boolean or function(name, value)
      Default: false

      Enables debug output. When set a function, this function will recieve a section name and its value.

    • tolerant

      Type: Boolean
      Default: false

      Enables tolerant parsing mode. This mode supresses parsing errors when possible.

    • stat

      Type: Boolean
      Default: false

      Enables stat mode. When mode is enabled a query stat interface is returning instead of resulting data.

    Query introspection

    To introspect a query, it should be compiled in "stat" (statistic) mode by passing a stat option. In this case a result of the query evaluation will be a special API with encapsulated state instead of a value:

    import jora from 'jora';
    const query = jora('...query...', { stat: true });
    const statApi = query(data);
    // { stat() { ... }, suggestion() { ... }, ... }

    The returned API allows fetching the values which are passed through a location in a query (the stat() method) as well as a list of suggestions for a location (the suggestion() method):

    import jora from 'jora';
    const query = jora('.[foo=""]', { stat: true });
    const statApi = query([{ id: 1, foo: "hello" }, { id: 2, foo: "world" }]);
    // [
    //   {
    //     context: 'path',
    //     from: 2,
    //     to: 5,
    //     text: 'foo',
    //     values: Set(2) { [Object], [Object] },
    //     related: null
    //   }
    // ]
    statApi.suggestion(3); // .[f|oo=""]
    // [
    //   {
    //     type: 'property',
    //     from: 2,
    //     to: 5,
    //     text: 'foo',
    //     suggestions: [ 'id', 'foo' ]
    //   }
    // ]
    statApi.suggestion(7); // .[foo="|"]
    // [
    //   {
    //     type: 'value',
    //     from: 6,
    //     to: 8,
    //     text: '""',
    //     suggestions: [ 'hello', 'world' ]
    //   }
    // ]

    That's an effective way to use stat mode together with tolerant mode for incomplete queries:

    import jora from 'jora';
    const query = jora('.[foo=]', {
        stat: true,
        tolerant: true // without the tolerant option a query compilation
                       // will raise a parse error:
                       // .[foo=]
                       // ------^
    const statApi = query([{ id: 1, foo: "hello" }, { id: 2, foo: "world" }]);
    statApi.suggestion(6); // .[foo=|]
    // [
    //   {
    //     type: 'value',
    //     from: 6,
    //     to: 6,
    //     text: '',
    //     suggestions: [ 'hello', 'world' ]
    //   },
    //   {
    //     type: 'property',
    //     from: 6,
    //     to: 6,
    //     text: '',
    //     suggestions: [ 'id', 'foo' ]
    //   }
    // ]


    • stat(pos: number, includeEmpty?: boolean)

      Returns an array of ranges with all the values which are passed through pos during performing a query.

      Output format:

          suggestion(): Array<{
              context: 'path' | 'key' | 'value' | 'in-value' | 'value-subset' | 'var',
              from: number,
              to: number,
              text: string,
              values: Set<any>,
              related: Set<any> | null
          }> | null
    • suggestion(pos: number, options?)

      Returns suggesion values grouped by a type or null if there is no any suggestions. The following options are supported (all are optional):

      • limit (default: Infinity) – a max number of the values that should be returned for each value type ("property", "value" or "variable")
      • sort (default: false) – a comparator function (should take 2 arguments and return a negative number, 0 or a positive number) for value list sorting, makes sence when limit is used
      • filter (default: function) – a filter function factory (pattern => value => <expr>) to discard values from the result when returns a falsy value (default is equivalent to patttern => value => String(value).toLowerCase().includes(pattern))

      Output format:

          suggestion(): Array<{
              type: 'property' | 'value' | 'variable',
              from: number,
              to: number,
              text: string,
              suggestions: Array<string | number>
          }> | null



    // single-line comment
    /* multi-line
    comment */


    Jora Description
    Hexadecimal numbers
    `template line1
    template line2`
    `template ${hello} ${world}`
    A JavaScript regexp, only i flag supported
    { } Object initializer/literal syntax. Spread operator (...) can be used, e.g. { a: 1, ..., } (... with no expression on right side the same as ...$)
    [ ] Array initializer/literal syntax. Spread operator (...) can be used, e.g. [1, ...,] (... with no expression on right side the same as ...$). Unlike JavaScript, spread operator in jora inlines arrays only and left as is any other values, i.e. [...[1, 2], ...3, ..."45", { "6": 7 }] -> [1, 2, 3, "45", { "6": 7 }]
    => e
    < block > (deprecated)
    A function
    NOTE: Syntax < block > is deprecated, avoid to use it
    query asc
    query desc
    query asc, query desc, ...
    A sorting function that takes two arguments and compare query result for each in specified order (asc – ascending, desc – descending)
    query ascN
    query descN
    The same as asc/desc but natural sorting
    query ascA
    query descA
    The same as asc/desc but reverse order for numbers
    query ascAN
    query descAN
    The same as asc/desc but natural sorting and reverse order for numbers


    Following keywords can be used with the same meaning as in JavaScript:

    • true
    • false
    • null
    • undefined
    • Infinity
    • NaN


    Jora Description
    x + y Add
    In case one of the operands is an array it produces new array with elements from `x` and `y` excluding duplicates
    x - y Subtract
    In case one of the operands is an array with elements from `x` excluding elements from `y`
    x * y Multiply
    x / y Divide
    x % y Modulo


    Jora Description
    x = y Equals (as === in JS)
    x != y Not equals (as !== in JS)
    x < y Less than
    x <= y Less than or equal to
    x > y Greater than
    x >= y Greater than or equal to
    x ~= y Match operator, behaviour depends on y type:
    RegExp – test against regexp
    function – test like filter()
    null or undefined – always truthy
    anything else – always falsy

    Boolean logic

    Jora Description
    ( x ) Explicity operator precedence. Definitions are allowed (i.e. ($a: 1; $a + $a) see bellow)
    x or y Boolean or.
    Equivalent to || in JS, but x tests with bool() method
    x and y Boolean and.
    Equivalent to && in JS, but x tests with bool() method
    not x
    no x
    Boolean not.
    Equivalent to && in JS, but x tests with bool() method
    x ? y : z If x is truthy than return y else return z. x tests with bool() method
    x in [a, b, c]
    [a, b, c] has x
    Equivalent to x = a or x = b or x = c
    x not in [a, b, c]
    [a, b, c] has no x
    Equivalent to x != a and x != b and x != c

    Block & definitions

    Some constructions suppose to use a block, which may consists of a variable definition list (should comes first) and an expression. Both are optional. When an expression is empty, a current value (i.e. $) returns.

    The syntax of definition (white spaces between any part are optional):

    $ident ;
    $ident : expression ;

    For example:

    $foo:123;          // Define `$foo` variable
    $bar;              // The same as `$bar:$.bar;` or `$a: bar;`
    $baz: $foo + $bar; // Definitions may be used in following expressions

    In terms of JavaScript, a block creates a new scope. Once a variable is defined, its value never change. Variables can be redefined in nested scopes, but can't be duplicated in the same scope - it causes to error.

    Special references

    Jora Description
    $ A scope input data (current value). On top level scope it's the same as @. In most cases it may be omitted. Used implicitly an input for subquery when no other subjects is defined (e.g. foo() and .foo() are equivalent for $.foo()).
    $$ A reference to the second parameter of closest function or undefined when no such
    @ A query input data
    # A query context

    Since Jora's query performs as query(data, context), in terms of Jora it looks like query(@, #).

    Path chaining

    jora Description
    ident The same as $.ident
    .ident Child member operator (example:,['use any symbols for name'])
    ..( block )
    Recursive descendant operator (example: ..deps, ..(deps + dependants))
    .[ block ] Filter a current data. Equivalent to a .filter(<block>)
    .( block ) Map a current data. Equivalent to a .map(<block>)
    Invoke a method to current value, where $method is a reference to definition value (i.e. $example: => $ * 10; 2.$plural(["example", "examples"])). Can take arguments (i.e. $method(one, 2)).
    Invoke a method to current value. See build-in methods below
    path[expr] Array-like notation to access properties. Behaves like pick() method. In case you need to fetch a value to each element of array use .($[expr]) or map(=>$[expr])
    Slice notation. Examples: $str: '<foo>'; str[1:-1] (result is 'foo') or $ar:[1,2,3,4,5,6]; $ar[-3::-1] (result is [6,5,4])
    expr | [definitions] expr | ... Pipeline operator. It's useful to make a query value as current value. Approximately this effect can be obtained using variables: $ar: [1,2,3]; { size: $ar.size(), top2: $ar[0:2] }. However, with pipeline operator it's a bit simplier and clear: `[1,2,3]

    Build-in methods

    jora Description
    bool() The same as Boolean() in JS, with exception that empty arrays and objects with no keys treats as falsy
    keys() The same as Object.keys() in JS
    values() The same as Object.values() in JS
    entries() Similar to Object.entries() in JS with a difference: { key, value } objects is using for entries instead of array tuples
    fromEntries() Similar to Object.fromEntries() in JS with difference: { key, value } objects are expecting as entries instead of array tuples
    Get a value by a key, an index or a function. It returns an element with e index for arrays, a char with e index for strings, and a value with e key (must be own key) for enything else. Negative indecies are supported for arrays and strings. Current value is element for an array, a char for a string or an entry value for object. Arg1 (i.e. $$) is an index for arrays and strings, and a key for objects.
    size() Returns count of keys if current data is object, otherwise returns length value or 0 when field is absent
    sort(<fn>) Sort an array by a value fetched with getter (<fn>). Keep in mind, you can use sorting function definition syntax using asc and desc keywords, qhich is more effective in many ways. In case of sorting function definition usage, < and > are not needed and you can specify sorting order for each component. Following queries are equivalents:
    sort(<>) and sort( asc)
    sort(<foo>).reverse() and sort(foo desc)
    sort(<[a, b]>) and sort(a asc, b asc)
    reverse() Reverse order of items
    group(<fn>[, <fn>]) Group an array items by a value fetched with first getter.
    filter(<fn>) The same as Array#filter() in JS
    map(<fn>) The same as Array#map() in JS
    split(pattern) The same as String#split() in JS. pattern may be a string or regexp
    join(separator) The same as Array#join() in JS. When separator is undefined then "," is using
    slice(from, to) The same as Array#slice() or String#slice() in JS
    match(pattern, matchAll?) Similar to String#match(). pattern might be a RegExp or string. When matchAll is truthy then returns an array of all occurrences of the pattern. Expressions match(/../g) and match(/../, true) are equivalent.
    reduce(fn[, initValue]) The same as Array#reduce() in JS. Use $$ to access to accumulator and $ to current value, e.g. find the max value reduce(=>$ > $$ ? $ : $$)




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