用于在不同目录中编译的 TypeScript API

Question

I have a typescript program that contains multiple .ts files. I want to compile those .ts to .js and place them in a different directory.

I'm inspired by the example from this page: https://github.com/Microsoft/TypeScript/wiki/Using-the-Compiler-API

function compile(fileNames, options) {
    let program = ts.createProgram(fileNames, options);
    let emitResult = program.emit();

    let allDiagnostics = ts
        .getPreEmitDiagnostics(program)
        .concat(emitResult.diagnostics);

    allDiagnostics.forEach(diagnostic => {
        if (diagnostic.file) {
            let {line, character} = diagnostic.file.getLineAndCharacterOfPosition(
                diagnostic.start
            );
            let message = ts.flattenDiagnosticMessageText(
                diagnostic.messageText,
                "\n"
            );
            console.log(
                `${diagnostic.file.fileName} (${line + 1},${character + 1}): ${message}`
            );
        } else {
            console.log(
                `${ts.flattenDiagnosticMessageText(diagnostic.messageText, "\n")}`
            );
        }
    });

    let exitCode = emitResult.emitSkipped ? 1 : 0;
    console.log(`Process exiting with code '${exitCode}'.`);
    process.exit(exitCode);
}

Then I use outDir in compiler options object

compile(["test.ts"], {
    noEmitOnError: false,
    noImplicitAny: false,
    target: ts.ScriptTarget.ES5,
    module: ts.ModuleKind.ESNext,
    outDir: "output" // files are placed in a directory called output
});

It works, however I'm curious if there's a different way to decide the location where to write the .js files that doesn't involve outDir property from compiler options.

Note: I'm looking for an answer that uses the typescript api and not the command line tsc

Answer 1

The second argument for emit() is writeFile?: WriteFileCallback . You can try to use it and implement writing files yourself in whatever way you need:

program.emit(undefined, yourOwnWriteFileFunction);

Also, according to comments and the code, ts.createProgram() accepts custom implementation for CompilerHost which also can override writeFile :

export interface CompilerHost extends ModuleResolutionHost {
    ....
    writeFile: WriteFileCallback;

Relevant part of Program interface

export interface Program extends ScriptReferenceHost {

    /**
     * Emits the JavaScript and declaration files.  If targetSourceFile is not specified, then
     * the JavaScript and declaration files will be produced for all the files in this program.
     * If targetSourceFile is specified, then only the JavaScript and declaration for that
     * specific file will be generated.
     *
     * If writeFile is not specified then the writeFile callback from the compiler host will be
     * used for writing the JavaScript and declaration files.  Otherwise, the writeFile parameter
     * will be invoked when writing the JavaScript and declaration files.
     */
    emit(targetSourceFile?: SourceFile, writeFile?: WriteFileCallback, cancellationToken?: CancellationToken, emitOnlyDtsFiles?: boolean, customTransformers?: CustomTransformers): EmitResult;

Note that these parts of API are not documented on the TypeScript wiki, so if you decide to use them you should keep an eye on breaking API changes page .