Typescript implementation of JMESPath with additional functionality for LetsFlow
npm install @letsflow/jmespath@letsflow/jmespath is a TypeScript implementation of the JMESPath spec.
JMESPath is a query language for JSON. It will take a JSON document
as input and transform it into another JSON document
given a JMESPath expression.
This fork extends the original specs, adding the following functionality;
* Custom functions
* Root value access
* Number literals
Additionally, it adds the following functions:
* if - Conditional expression
* range - Generate a range of numbers or prefixed strings
* to_object - Convert an array of key-value pairs into an object
* json_serialize - Serialize a JSON value to a string
* json_parse - Parse a JSON string into a JSON object
* sha256 - Calculate the SHA-256 hash of a string
* sha512 - Calculate the SHA-512 hash of a string
* uuid - Generate a UUID v5
* regex_test - Test if a string matches a regular expression
* regex_match - Return the first match of a regular expression in a string
* regex_match_all - Return all matches of a regular expression in a string
* regex_replace - Replace parts of a string matching a regular expression with a replacement string
``
npm install @letsflow/jmespath
`javascript
import { search } from '@letsflow/jmespath';
search(
{ foo: { bar: { baz: [0, 1, 2, 3, 4] } } },
"foo.bar.baz[2]"
);
// OUTPUTS: 2
`
In the example we gave the search function input data of{foo: {bar: {baz: [0, 1, 2, 3, 4]}}} as well as the JMESPathfoo.bar.baz[2]
expression , and the search function evaluated2
the expression against the input data to produce the result .
The JMESPath language can do a lot more than select an element
from a list. Here are a few more examples:
`javascript
import { search } from '@letsflow/jmespath';
const document = {
foo: {
bar: {
baz: [0, 1, 2, 3, 4]
}
}
};
search(document, "foo.bar");
// OUTPUTS: { baz: [ 0, 1, 2, 3, 4 ] }
`
`javascript
import { search } from '@letsflow/jmespath';
const document = {
"foo": [
{ "first": "a", "last": "b" },
{ "first": "c", "last": "d" }
]
};
search(document, "foo[*].first")
// OUTPUTS: [ 'a', 'c' ]
`
`javascript
import { search } from '@letsflow/jmespath';
const document = {
"foo": [
{ "age": 20 },
{ "age": 25 },
{ "age": 30 },
{ "age": 35 },
{ "age": 40 }
]
}
search(document, "foo[?age > 30]");`
// OUTPUTS: [ { age: 35 }, { age: 40 } ]
You can precompile all your expressions ready for use later on. the compile
function takes a JMESPath expression and returns an abstract syntax tree that
can be used by the TreeInterpreter function
`javascript
import { compile, TreeInterpreter } from '@jmespath-community/jmespath';
const ast = compile('foo.bar');
TreeInterpreter.search(ast, { foo: { bar: 'BAZ' } })
// RETURNS: "BAZ"
`
#### registerFunction(functionName: string, customFunction: RuntimeFunction, signature: InputSignature[]): void
Extend the list of built-in JMESpath expressions with your own functions.
`javascript
import {search, registerFunction, TYPE_NUMBER} from '@letsflow/jmespath'
search({ foo: 60, bar: 10 }, 'divide(foo, bar)')
// THROWS ERROR: Error: Unknown function: divide()
registerFunction(
'divide', // FUNCTION NAME
(resolvedArgs) => { // CUSTOM FUNCTION
const [dividend, divisor] = resolvedArgs;
return dividend / divisor;
},
[{ types: [TYPE_NUMBER] }, { types: [TYPE_NUMBER] }] //SIGNATURE
);
search({ foo: 60, bar: 10 }, 'divide(foo, bar)');
// OUTPUTS: 6
`
Optional arguments are supported by setting {..., optional: true} in argument signatures
`javascript
registerFunction(
'divide',
(resolvedArgs) => {
const [dividend, divisor] = resolvedArgs;
return dividend / divisor ?? 1; //OPTIONAL DIVISOR THAT DEFAULTS TO 1
},
[{ types: [TYPE_NUMBER] }, { types: [TYPE_NUMBER], optional: true }] //SIGNATURE
);
search({ foo: 60, bar: 10 }, 'divide(foo)');
// OUTPUTS: 60
`
Use $ to access the document root.
`javascript
search({foo: { bar: 999 }, baz: [1, 2, 3]}, '$.baz[*].[@, $.foo.bar]')
// OUTPUTS:
// [ [ 1, 999 ], [ 2, 999 ], [ 3, 999 ] ]
`
Numbers in the root scope are treated as number literals. This means that you don't
need to quote numbers with backticks.
`javascript
search([{"bar": 1}, {"bar": 10}], '[?bar==10]')
// OUTPUTS;
// [{"bar": 10}]
`
You can also use numbers in arithmetic operations
`
search({}, '16 + 26'); // 42
jmespath
if(condition, thenValue, elseValue?)
`Description:
Returns
if condition is true, otherwise returns elseValue. If elseValue is not provided, it defaults to null.Example:
`jmespath
if(@ > 10, "large", "small")
`$3
Syntax:
jmespath
get(object, key, defaultValue?)
`Description:
Returns the value of a key in an object.
Example:
jmespath
get({ key: 'value' }, 'key') // "value"
get({ key: 'value' }, 'missing') // null
get({ key: 'value' }, 'missing', 'default') // "default"
`$3
Syntax:
jmespath
range(start, end, prefix?)
`Description:
Generates an array of numbers or prefixed strings from
to end - 1. If prefix is provided, each number is prefixed.Example:
`jmespath
range(5) // [0, 1, 2, 3, 4]
range(1, 5) // [1, 2, 3, 4]
range(1, 5, 'item_') // ["item_1", "item_2", "item_3", "item_4"]
`$3
Syntax:
jmespath
to_object(entries)
`Description:
Converts an array of key-value pairs into an object.
Example:
jmespath
to_object([['key1', 'value1'], ['key2', 'value2']])
// { "key1": "value1", "key2": "value2" }[ 'value1', 'value2'] | to_object(zip(range(1, length(@) + 1, 'key'), @))
// { "key1": "value1", "key2": "value2" }
`$3
Syntax:
jmespath
json_serialize(value)
`_Uses a deterministic version of JSON.stringify to serialize the value._
Description:
Serializes a JSON value to a string.
Example:
jmespath
json_serialize({ key: 'value' })
// "{\"key\":\"value\"}"
`$3
Syntax:
jmespath
json_parse(string)
`Description:
Parses a JSON string into a JSON object.
Example:
jmespath
json_parse("{\"key\":\"value\"}")
// { "key": "value" }
`$3
Syntax:
jmespath
sha256(string)
`Description:
Calculates the SHA-256 hash of a string and returns it as a hexadecimal string.
Example:
jmespath
sha256('hello')
// "2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824"
`$3
Syntax:
jmespath
sha512(string)
`Description:
Calculates the SHA-512 hash of a string and returns it as a hexadecimal string.
Example:
jmespath
sha512('hello')
// "9b71d224bd62f3785d96d46ad3ea3d73319b0c44e59b202205c5d235a0a6caa5a3b36f8c0ab9d45df9215bf07d4d1552c0b1f8bd2671c8a7a3d126f457d79d72"
`$3
Syntax:
jmespath
uuid(name?, namespace?)
`Description:
Generates a version 5 UUID.
UUID v5 is consistent. It creates a UUID based on the SHA hash of the input. This means that any given combination
of input and namespace will result in the same UUID, every time.
Example:
jmespath
uuid('example') // v5 UUID
uuid('example', '6ba7b810-9dad-11d1-80b4-00c04fd430c8') // v5 UUID with namespace
` must be a string. Use json_serialize() to convert a JSON object to a string.
namespace must be a UUID string. By default, it uses the NIL UUID.The UUID RFC pre-defines four namespaces
* NameSpace_DNS:
6ba7b810-9dad-11d1-80b4-00c04fd430c8
* NameSpace_URL:
* NameSpace_OID:
* NameSpace_X500: $3
Syntax:
jmespath
regex_test(regex, string)
`Description:
Tests if a string matches a given regular expression.
Example:
jmespath
regex_test('/^hello/', 'hello world') // trueregex_test('/^hello/', 'HELLO world') // false
regex_test('/^hello/i', 'HELLO world') // true
`$3
Syntax:
jmespath
regex_match(regex, string)
`Description:
Returns the first match of a regular expression in a string as an array.
Example:
jmespath
regex_match('/hello (\\w+)/', 'hello world')
// ["hello world", "world"]regex_match('/\\w+/g', 'hello world')
// ["hello", "world"]
`$3
Syntax:
jmespath
regex_match_all(regex, string)
`Description:
Returns all matches of a regular expression in a string as an array of arrays.
Example:
jmespath
regex_match_all('/(\\w+)=(\d+)/g', 'foo=24 bar=99')
// [["foo=24", "foo", "24"], ["bar=99", "bar", "99"]]
`$3
Syntax:
jmespath
regex_replace(regex, replacement, string)
`Description:
Replaces parts of a string matching a regular expression with a replacement string.
Example:
jmespath
regex_replace('/world/', 'universe', 'hello world')
// "hello universe"
`$3
Syntax:
jmespath
regex_count(regex, string)
`Description:
Counts the number of matches of a regular expression in a string.
Example:
jmespath
regex_count('/\\w+/g', 'hello world')
// 2
``The example above only shows a small amount of what
a JMESPath expression can do. If you want to take a
tour of the language, the best place to go is the
JMESPath Tutorial.
The full JMESPath specification can be found
on the JMESPath site.