Transpile TypeScript In Memory With Node

Question

Is there a way to transpile TypeScript in memory with Node? I would like to be able to get the generated JavaScript in memory.

You can load the compiler into node, which modules like gulp-typescript do. Not sure if they operate fully in-memory. — ssube
– ssube, Commented Feb 25, 2015 at 21:22
Assuming by "in memory" you just mean "not written to a file" then yeah, you can use gulp-tsc to compile the TypeScript and then pipe it anywhere you want. I'm sure there are tons of examples of this online, but if you'd liek an example- here's one of my gulpfiles that uses gulp-tsc: github.com/bvaughn/task-runner/blob/master/gulpfile.js#L97 — bvaughn
– bvaughn, Commented Feb 25, 2015 at 21:35
Transpile it to a file, read it into memory and delete the file — pouya
– pouya, Commented May 16, 2019 at 10:26

basarat · Accepted Answer · 2020-05-12 15:09:44Z

11

Yes. TypeScript provides a a ts.transpileModule function:

const ts = require('typescript');
const source = "let x: string  = 'hello world'";
const result = ts.transpileModule(source, { compilerOptions: { module: ts.ModuleKind.CommonJS }});
console.log(result.outputText); // var x = 'hello world';

More

From the TypeScript wiki : https://github.com/microsoft/TypeScript/wiki/Using-the-Compiler-API#a-simple-transform-function

edited May 12, 2020 at 15:09

answered Feb 25, 2015 at 23:42

basarat

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mvermand Over a year ago

Typescript-Simple is no longer maintained.

A2MetalCore · Accepted Answer · 2016-02-12 17:21:56Z

We ended up developing our own solution based on the native TypeScript transpileModule functionality.

FROM TYPESCRIPT DOCS

TranspileModule will compile source text from 'input' argument using specified compiler options. If no options are provided - it will use a set of default compiler options. Extra compiler options that will unconditionally be used by this function are:

isolatedModules = true
allowNonTsExtensions = true
noLib = true
noResolve = true

transpile() - This code will transpile TypeScript to JavaScript (typescriptServices.min.js from TypeScript is required):

export function transpile(tscode: string): TYPE.EVENT {

    interface TranspileOptions {
        compilerOptions?: any
        fileName?: string;
        reportDiagnostics?: boolean;
        moduleName?: string;
        renamedDependencies?: any;
    }

    interface TranspileOutput {
        outputText: string;
        diagnostics?: any[];
        sourceMapText?: string;
    }

    let compilerOptions: ts.CompilerOptions = {
        isolatedModules: false
    }

    let options: TranspileOptions = {
        compilerOptions: compilerOptions,
        reportDiagnostics: true
        // moduleName: modulename
    }

    let info: TYPE.EVENT;

    try {

        // Transpile the ts code to js.
        let ret: TranspileOutput = ts.transpileModule(tscode, options);

        // If diagnostics were returned.
        // NOTE: The transpiler is currently always return a message (code=5047) about 'isolatedModules', which
        // is not relavent for our use. If there is more than one row than there is in fact an error.
        if (ret.diagnostics && ret.diagnostics.length > 0) {

            let code = ret.diagnostics[0].code;

            if (code == 5047) {
                return (info = {
                    success: true,
                    returnvalue: ret.outputText,
                    caller: LibCore.getFunctionName(arguments)
                })
            } else {

                let text = ret.diagnostics[0].messageText;
                // let hint = ret.diagnostics[0].file.parseDiagnostics[0].file.nextContainer.symbol.name;

                return (info = {
                    success: false,
                    returnvalue: ret.diagnostics,
                    message: `Syntax error: ${text} Code: ${code}`,
                    caller: LibCore.getFunctionName(arguments)
                })
            }

        } else {
            return (info = {
                success: true,
                returnvalue: ret.outputText,
                caller: LibCore.getFunctionName(arguments)
            })
        }

    } catch (e) {
        return (info = {
            success: false,
            message: e.message,
            caller: LibCore.getFunctionName(arguments)
        })
    }
}

Cool. Do you know how to get the definitions .d.ts output from the API?

Danon · Accepted Answer · 2024-03-10 11:59:07Z

0

Not exactly an answer to the question, but if your main reason for wanting to try in-memory compiler is performance, what worked for me was resetting types and lib in compilerOptions.

const program: ts.Program = createProgram([entryFile], {
  types: [],
  lib: [],
});

My build speedup from 10 seconds to 100ms. I didn't need external types and libs in my project, so that was an easy fix for me.

answered Mar 10, 2024 at 11:59

Danon

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