Expression Expander

Expands \\${to be evaluated} expressions in object graphs. The actual expression syntax inside of the \\${evaluated} is not defined within this module (only simple key lookup)

example

file.js

``js
import { createContext } from "expression-expander";

const context = createContext();

context.properties = { aKey: "aValue", moreKeys: { a: 1, b: 2 } };

// expanding whole expressions at the key position
console.log(
JSON.stringify(
context.expand({ simple: "${aKey}", complex: { "${moreKeys}": {} } })
)
);
`

Output

`json
{ "simple": "aValue", "complex": { "a": 1, "b": 2 } }
`

Any Object of the following types may be expanded

* String
* Number
* BigInt
* Buffer
* Object (key and value will be expanded)
* Array
* Map (key and value will be expanded)
* Set
* Boolean
* Promise

API

$3

* Evaluator
* Parameters
* PathEntry
* Properties
* Quoter
* Parameters
* Expander
* Parameters
* ExpressionExpander
* Properties
* createContext
* Parameters
* expand
* Parameters
* properties

Evaluator

Type: Function

$3

* expression string
* context Object
* path \[PathEntry]

Returns Object expression evaluation result

PathEntry

Type: Object

$3

* value Object

Quoter

Type: Function

$3

* value string to be quoted

Returns string quoted value

Expander

Type: Function

$3

* value (string | boolean | number | bigint | Object | Map | Set)
* path Array<PathEntry>?

Returns (string | boolean | number | bigint | Object | Map | Set) expression evaluation result

ExpressionExpander

Type: Object

$3

* properties Object
* expand Expander

createContext

Creates a new expansion context

$3

* options Object? object with the following keys

* options.leftMarker string? lead in of expression
* options.rightMarker string? lead out of expression
* options.markerRegexp (RegExp | string)? expression with lead in / out
* options.valueQuoter Quoter? to quote expanded values
by default no special quoting is done and the evaluated result will be direcly
inserted into the output string
* options.evaluate Evaluator? evaluate(expression,context,path) function to evaluate expressions
the default evaluation function does a lookup into the properties
* options.keepUndefinedValues boolean? true: is expression resolves to undefind the original string will be used (with surrounding ${})
* options.maxNestingLevel number? max number of recursive calls to expand defaults to 20
* options.properties Object? default properties to evaluate expression against

Returns ExpressionExpander newly created expansion context

expand

Type: Expander

$3

* object
* path (optional, default [{value:object}])

properties

Properties used for the default expander implementation

install

With npm do:

`shell
npm install expression-expander
``

license

BSD-2-Clause