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

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

{ "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

Table of Contents

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

Evaluator

Type: Function

Parameters

• expression string
• context Object
• path [PathEntry]

Returns Object expression evaluation result

PathEntry

Type: Object

Properties

• value Object

Quoter

Type: Function

Parameters

• value string to be quoted

Returns string quoted value

Expander

Type: Function

Parameters

• 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

Properties

• properties Object
• expand Expander

createContext

Creates a new expansion context

Parameters

• 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

Parameters

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

properties

Properties used for the default expander implementation

install

With npm do:

npm install expression-expander

license

BSD-2-Clause