Tokenizers, parsers and expression calculators in Node.js / ES2017

This module is a part of the Pip.Services polyglot microservices toolkit. It provides syntax and lexical analyzers and expression calculator optimized for repeated calculations.

The module contains the following packages:

• Calculator - Expression calculator
• CSV - CSV tokenizer
• IO - input/output utility classes to support lexical analysis
• Mustache - Mustache templating engine
• Tokenizers - lexical analyzers to break incoming character streams into tokens
• Variants - dynamic objects that can hold any values and operators for them

Quick links:

• API Reference
• Change Log
• Get Help
• Contribute

Use

Install the NPM package as

npm install pip-services4-expressions-node --save

The example below shows how to use expression calculator to dynamically calculate user-defined expressions.

import { IConfigurable } from 'pip-services4-commons-node';
import { ConfigParams } from 'pip-services4-commons-node';
import { IReferenceable } from 'pip-services4-commons-node';
import { IReferences } from 'pip-services4-commons-node';
import { Descriptor } from 'pip-services4-commons-node';
import { IOpenable } from 'pip-services4-commons-node';

...
let calculator = new ExpressionCalculator();

calculator.expression = "A + b / (3 - Max(-123, 1)*2)";

let vars = new VariableCollection();
vars.add(new Variable("A", new Variant(1)));
vars.add(new Variable("B", new Variant("3")));

let result = await calculator.evaluateWithVariables(vars);
console.log("The result of the expression is " + result.asString);
...

This is an example to process mustache templates.

let mustache = new MustacheTemplate();
mustache.template = "Hello, {{{NAME}}}{{#ESCLAMATION}}!{{/ESCLAMATION}}{{#unless ESCLAMATION}}.{{/unless}}";
let result = mustache.evaluateWithVariables({ NAME: 'Mike', ESCLAMATION: true });
console.log("The result of template evaluation is '" + result + "'");

Develop

For development you shall install the following prerequisites:

• Node.js 8+
• Visual Studio Code or another IDE of your choice
• Docker
• Typescript

Install dependencies:

npm install

Compile the code:

tsc

Run automated tests:

npm test

Generate API documentation:

./docgen.ps1

Before committing changes run dockerized build and test as:

./build.ps1
./test.ps1
./clear.ps1

Contacts

The module is created and maintained by Sergey Seroukhov and Danil Prisyazhniy.