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NCalc is a mathematical expressions evaluator in JavaScript/TypeScript. NCalc can parse anyexpression and evaluate the result, including static or dynamic parameters and custom functions. Youmay also want to look at the example running on CloudFlare workershttps://github.com/ThomasHambach/expression.worker

In theory, all browsers supporting ECMAScript 5.1.

In practice, this target has been extensively tested against:

• Firefox 34.0.5
• Safari 8.0.2
• Chrome 39.0.2171
• Explorer 11.0.3

The package has been extensively tested against Node.js 14 LTS.

Get the package from npm.org (https://www.npmjs.com/package/ncalcjs) by running

npm i --s ncalcjs

or with yarn

yarn ncalcjs

For documentation here is the table of content:

• description: overall concepts, usage and extensibility points
• operators: available standard operators and structures
• functions: list of already implemented functions
• parameters: on how to use parameters expressions

import{Expression}from'ncalcjs';conste=newExpression('2 + 3 * 5');console.log(e.Evaluate());// 17

The API compared to C# NCalc is a little different. In NCalcJS you define custom functions in thefollowing way. Each function is expected to be of the typeEvaluateFunctionHandler.

conste=newExpression('SecretOperation(3, 6)');e.EvaluateFunction['SecretOperation']=(args:FunctionArgs)=>{args.Result=args.Parameters[0].Evaluate()+args.Parameters[1].Evaluate();};console.log(e.Evaluate());// 9

You can use the methodExpression.HasErrors() to check for any errors that are present in yourexpression. The errors details are stored inExpression.errors.

import{Expression}from'ncalcjs';conste=newExpression('2 + 3 * 5');if(e.HasErrors()){console.error(e.errors);}

• Round does not return the correct value

Install all dependencies

npm install

Before we can run our build, we need to installts-patch that will change ourpaths configuredintsconfig.json. Note that you have to run this every time after runningnpm install.

npm run prepare

Build the distribution version

npm run build

Note that the files, except forNCalc.g4 in/src/Grammar are automatically generated. Anychanges you wish to make there are to be made inNCalc.g4. You will need Java runtime installed onyour system to generate these files.

To update the generated files, run this commond inside/src/Grammar.

antlr4 -Dlanguage=TypeScript NCalc.g4

Special thanks to:

• Thaina for creating the basis of this package's ANTLR4 grammarfile. Original C# version available at:https://github.com/Thaina/NCalc2/blob/master/grammer/NCalc.g
• robmarti12 for implementing the staticCompile as in original NCalc.

NCalc C# implementation.

Pure asynchronous C# implementation of NCalc byPeter Liljenberg.

Extension functions for NCalc in C# to handle many general functions,
including string functions, switch, if, in, typeOf, cast etc.
Developed by David, Dan and all atPanoramic Data.

Starter kit to run NCalcJS in a cloudflare worker.