Node read ts module / read code file

Question

How do you read the classes from a file?

.src/my-a.service.ts

export class MyAService {
    ...
}

.src/my-b.service.ts

export class MyBService {
    ...
}

./read-modules.js

const fs = require('fs');
const _ = require('lodash');

let files = fs.readdirSync('./src')
    .filter(item => {
        return _.includes(item, '.service.ts')
    });


files.forEach(item => {
    // get ['MyAService', 'MyBService']
});

I know you could do some string parsing but is there a high level way to read js/ts exports from a file(not import the code but just get the names of the exported classes).

Edit 1: There is X number of *.service.ts files my-a.service.ts and my-b.service.ts are just examples. I'm not trying to import or require these classes to use them in code just get the class names for code generation.

Edit 2: I looks like tsreflect-compiler is what I need:

const fs = require('fs');
const _ = require('lodash');
const compiler = require('tsreflect-compiler');

let files = fs.readdirSync('./src')
    .filter(item => {
        return _.includes(item, '.service.ts')
    });


let mods = new Map();
files.forEach(item => {
    let diag = compiler.compile(
        [`./src/${item}`],
        {
            noLib: false,
            suppressImplicitAnyIndexErrors: true,
            noImplicitAny: false,
            module: 'ES2015',
            moduleResolution: 'Node',
            target: 'ES5'
        },
        {
            readFile: (filename, onError) => {
                let text;
                try {
                    text = fs.readFileSync(filename, 'utf8');
                } catch (error) {
                    if (onError) {
                        onError(e.message);
                    }
                    text = '';
                }
                return text;
            },
            writeFile: (fileName, data, writeByteOrderMark, onError) => {
                mods.set(item, JSON.parse(data).declares.map(d => d.name));
            }
        }
    );
});

mods.forEach((value, key) => {
    console.log(key); // my-a.service.ts
    console.dir(value); // [ 'MyAService' ]
});

However tsreflect-compiler only uses TypeScript 1.4 compiler and I need 2.x newer. Is there a more modern solution?

Answer 1

This ended up being my solution:

const fs = require('fs');
const _ = require('lodash');
const ts = require('typescript');

let files = fs.readdirSync('./src')
    .filter(item => _.includes(item, '.service.ts'));

let mods = new Map();
files.forEach(file => {
    let ex = [];
    // https://github.com/Microsoft/TypeScript/wiki/Using-the-Compiler-API#using-the-type-checker
    // Build a program using the set of root file names in fileNames
    let program = ts.createProgram(
        [`./src/${file}`],
        {
            module: ts.ModuleKind.ES2015,
            moduleResolution: ts.ModuleResolutionKind.NodeJs,
            target: ts.ScriptTarget.ES5
        }
    );
    // Get the checker, we will use it to find more about classes
    let checker = program.getTypeChecker();
    // Visit every sourceFile in the program
    program.getSourceFiles()
        .filter(sourceFile => _.includes(sourceFile.fileName, file))
        .forEach(sourceFile => {
            // Walk the tree to search for classes
            ts.forEachChild(sourceFile, node => {
                if (node.kind === ts.SyntaxKind.ClassDeclaration) {
                    // This is a top level class, get its symbol
                    let symbol = checker.getSymbolAtLocation(node.name);
                    ex.push(symbol.getName());
                }
            });
        });
    mods.set(file, ex);
});

mods.forEach((value, key) => {
    console.log(key); // my-a.service.ts
    console.dir(value); // [ 'MyAService' ]
});

Answer 2

Not sure what you're use case is but the easiest way would be -

const serviceA = require('./MyAService');
const keys = Object.keys(serviceA);

If not, you'd have to read in the file with fs and then do some string matching/regex to find all of the exported function which could be very tricky.

Answer 3

Since Javascript/ES6 doesn't actually have classes, you shouldn't be relying on class names.

What you are looking for is named exports:

exports.MyBService = class MyBService {
    ...
}

That way you can do

const allServices = require('./myservices')
console.log(Object.keys(allServices))

Answer 4

In node.js, you would export files using the commonjs format for javascript files.

Basic Example for js

const someModule = require('./someModule');

const methods = param => { return param; };

modules.exports = { methods }

Typescript gets to use the new es6 format, but you need to setup your typescript compiler for it to work with node.

import someClass from './someClass';
someClass.method();
export class name { .. }

Answer 5

use typescript-require To get ts file object in js

https://www.npmjs.com/package/typescript-require