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Lambda2Js

This is an ExpressionTree (lambda) to Javascript converter.

It is portable, so that you can use it in most environments.

Its purpose is to convert a C# expression tree (from Linq name space) to a syntactically correct javascript code.

It can be extended to customize the mapping of expressions:

  • support custom static methods, instead of emitting code that would otherwise depend on external Javascript
  • support custom types, converting method calls and properties accordingly

It is well tested, and won't break. More than 140 tests passing.

This project uses Semantic versioning.

Installing NuGet package:

PM> Install-Package Lambda2Js

Samples

Converting lambda with boolean and numeric operations:

Expression<Func<MyClass, object>> expr = x => x.PhonesByName["Miguel"].DDD == 32 || x.Phones.Length != 1;
var js = expr.CompileToJavascript();
// js = PhonesByName["Miguel"].DDD===32||Phones.length!==1

Converting lambda with LINQ expression, containing an inner lambda:

Expression<Func<MyClass, object>> expr = x => x.Phones.FirstOrDefault(p => p.DDD > 10);
var js = expr.CompileToJavascript();
// js = System.Linq.Enumerable.FirstOrDefault(Phones,function(p){return p.DDD>10;})

Converting lambda with Linq Select method:

Expression<Func<string[], IEnumerable<char>>> expr = array => array.Select(x => x[0]);
var js = expr.CompileToJavascript(
    new JavascriptCompilationOptions(
        JsCompilationFlags.BodyOnly | JsCompilationFlags.ScopeParameter,
        new[] { new LinqMethods(), }));
// js = array.map(function(x){return x[0];})

Clone using ToArray and targeting ES6:

Expression<Func<string[], IEnumerable<string>>> expr = array => array.ToArray();
var js = expr.Body.CompileToJavascript(
    ScriptVersion.Es60,
    new JavascriptCompilationOptions(new LinqMethods()));
// js = [...array]

Developing custom plugins

You can develop and use some built-in plugins. See the readme.md in the Plugins folder.

Building and testing

ATENTION! Please, run the ProjectsGenerator before doing any of these:

  • build the signed assembly

  • running tests for specific frameworks

    Run Projects Generator

Due to current Visual Studio limitations, I had to create a project generator to create some of the csproj files:

  • Lambda2Js.Signed.csproj is generated using the Lambda2Js.csproj as it's template. It will copy the package version to the FileVersion and to the AssemblyVersion fields to keep them consistent. Also, it adds the ".Signed" string where appropriate in file names and in project name, and finally it includes a reference to the snk file.

  • Lambda2Js.Tests.$(TargetFramework).csproj are generated from Lambda2Js.Tests.csproj. That is needed because this project is a multitargeted test project, and Visual Studio cannot see the tests inside after compiling it... so what I did was: create copy projects that have only one target framework for each of the possible targets.

Testing

To test support on the .Net 4.0, you need to run the Test.Net-v4.0.csproj because this framework version does not support the native test attributes to do automatic testing.

To test other framework versions, please, take a look at the TargetedTests solution folder. In that folder you will find all the tests. Unload all of them, but keep the framework version you want to test, then build it. Visual Studio will see the newly built tests and will list them. If the other frameworks test projects are not unloaded, Visual Studio may or may not list them.

Errors while building test projects

Make sure to NOT LOAD MORE THAN ONE test project inside the TargetedTests solution folder.

  • Load a single test project

    Load Single Test Project

  • Update Test Framework Packages

    Update Test Framework Packages