Syntax when calling Typescript class from Javascript

Question

I've written a typescript class that will be called in legacy javascript. I import it via:

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

After the transpile I end up with:

var ConfigurationManager = /** @class */ (function () {
    function ConfigurationManager

so it must be called with:

new ConfigurationManager.ConfigurationManager(...)

to create a new instance. Is there a way to clean this up so the javascript side is a little less verbose?

Titian Cernicova-Dragomir · Accepted Answer · 2017-12-07 15:41:01Z

3

There are several options:

You could just define another variable in which you put the class:

Code:

const ConfigurationManagerModule = require('./ConfigurationManager');
const ConfigurationManager = ConfigurationManagerModule.ConfigurationManager;
new ConfigurationManager(...);

You could set the whole export of the module as the class if the module exports nothing but this class.

Code:

export = class ConfigurationManager  {

}
const ConfigurationManager = require('./ConfigurationManager');

new ConfigurationManager();

For the second option, the difference between export class .. and export = class ..., is that in the first case we specify something to add to the export, in the second we specify that the whole export is the class. In terms of the generated JS, the first options generates this:

var ConfigurationManager = /** @class */ (function () {
    function ConfigurationManager() {
    }
    return ConfigurationManager;
}());
exports.ConfigurationManager = ConfigurationManager;

while the second generates this:

module.exports = /** @class */ (function () {
    function ConfigurationManager() {
    }
    return ConfigurationManager;
}());

edited Dec 7, 2017 at 15:41

answered Dec 7, 2017 at 15:32

Titian Cernicova-Dragomir

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3 Comments

Anthony Over a year ago

(1) is what I'm using atm. For (2) what is the difference between export = class and my current export class

Anthony Over a year ago

So playing with it and reading the doc, without the equals the file name operates similar to a namespace, you could export multiple classes within the 'filename'. With the equals you would get a single-object-per-file behavior?

Anthony Over a year ago

For future reference: After using the equals export you'll get: resolves to a non-module entity and cannot be imported using this construct. in the previously working typescript code that uses the class. You'll have to import with: import Configuration = require('./Configuration'); typescriptlang.org/docs/handbook/modules.html

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