What is the best way to merge import all with different elements?

Question

What is the best way to merge import all with different elements?

My TSLint is flagging the following issue:

Multiple imports from 'moment' can be combined into one.

Here is the code causing the problem:

import * as moment from 'moment';
import { Moment } from 'moment';

I have attempted various solutions without success (I couldn't find a relevant example in the documentation):

import * as moment, { Moment } from 'moment';
import { * as moment, Moment } from 'moment';
import { * as moment, Moment as Moment } from 'moment';

typescript

Answer 1

Answer №1

Caution: Be mindful because:

import * as moment from 'moment'

differs from

import moment from 'moment'

When using the second syntax, you are only importing the namespace moment and its contents, whereas the first syntax imports everything, including the function moment() that is outside of the namespace. The correct way to import is:

import * as moment from 'moment';
type Moment = moment.Moment;

Answer 2

Caution: Be mindful because:

import * as moment from 'moment'

differs from

import moment from 'moment'

When using the second syntax, you are only importing the namespace moment and its contents, whereas the first syntax imports everything, including the function moment() that is outside of the namespace. The correct way to import is:

import * as moment from 'moment';
type Moment = moment.Moment;

Answer 3

Answer №2

By using an asterisk in the import statement, you are able to access all elements from the imported module under a specified name using the as keyword.

For example:

import * as data from 'data';

In this scenario, there is no need to separately import { Data }, as you can directly access it by using data.Data.

Important Note:

It's not possible to combine the asterisk import with any other type of import. Additionally, in some cases like this one, the TSLint message might be slightly misleading.

UPDATE

Another way that should work (and indeed does work) in ES6 is:

import data, { Data } from 'data';

This feature was introduced in TypeScript version 1.8, as mentioned in the release notes.

Module loaders such as SystemJS encapsulate CommonJS modules and present them as default ES6 imports. This divergence in module presentation makes it challenging to share definition files between the SystemJS and CommonJS versions of the module, since their shapes differ based on the loader being used.

The new compiler flag --allowSyntheticDefaultImports indicates that the module loader performs a form of synthetic default import member creation which isn't explicitly stated in the imported .ts or .d.ts files. The compiler infers the existence of a default export matching the shape of the entire module itself.

System modules have this flag enabled by default.

Answer 4

By using an asterisk in the import statement, you are able to access all elements from the imported module under a specified name using the as keyword.

For example:

import * as data from 'data';

In this scenario, there is no need to separately import { Data }, as you can directly access it by using data.Data.

Important Note:

It's not possible to combine the asterisk import with any other type of import. Additionally, in some cases like this one, the TSLint message might be slightly misleading.

UPDATE

Another way that should work (and indeed does work) in ES6 is:

import data, { Data } from 'data';

This feature was introduced in TypeScript version 1.8, as mentioned in the release notes.

Module loaders such as SystemJS encapsulate CommonJS modules and present them as default ES6 imports. This divergence in module presentation makes it challenging to share definition files between the SystemJS and CommonJS versions of the module, since their shapes differ based on the loader being used.

The new compiler flag --allowSyntheticDefaultImports indicates that the module loader performs a form of synthetic default import member creation which isn't explicitly stated in the imported .ts or .d.ts files. The compiler infers the existence of a default export matching the shape of the entire module itself.

System modules have this flag enabled by default.

Answer 5

Answer №3

Sometimes the following method may not be effective. It all relies on whether someModule has a defined default export. If it does, then this method will work.

import someModule, { someMember } from 'someModule';

The specific module I was referring to did not have a defined default, so I opted for an alternate approach:

import * as someModule from 'someModule';
// To prevent importing multiple times from the same module, destructure the exported members from the module.
const { someMember } = someModule;

Answer 6

Sometimes the following method may not be effective. It all relies on whether someModule has a defined default export. If it does, then this method will work.

import someModule, { someMember } from 'someModule';

The specific module I was referring to did not have a defined default, so I opted for an alternate approach:

import * as someModule from 'someModule';
// To prevent importing multiple times from the same module, destructure the exported members from the module.
const { someMember } = someModule;

Answer 7

Answer №4

Typescript offers the flexibility to export multiple functions, classes, and variables from a single file. While most imports target specific elements, there are exceptions like importing Moment:

import * as moment from "moment";

This approach is also applicable when importing Angular:

import * as AngularCore from "@angular/core";

@AngularCore.Component({
    //...

By assigning all exports to a variable (e.g., AngularCore or moment), it creates a wrapper similar to a JavaScript object:

var AngularCore = {
    Component: // component details...
    OnInit: // OnInit interface details...
}

For a visual representation, refer to this diagram for better understanding:

https://i.sstatic.net/Okc77.png

You have the liberty to choose any name for the variable (like in the moment example).

If you're still confused, feel free to ask for clarification.

Answer 8

Typescript offers the flexibility to export multiple functions, classes, and variables from a single file. While most imports target specific elements, there are exceptions like importing Moment:

import * as moment from "moment";

This approach is also applicable when importing Angular:

import * as AngularCore from "@angular/core";

@AngularCore.Component({
    //...

By assigning all exports to a variable (e.g., AngularCore or moment), it creates a wrapper similar to a JavaScript object:

var AngularCore = {
    Component: // component details...
    OnInit: // OnInit interface details...
}

For a visual representation, refer to this diagram for better understanding:

https://i.sstatic.net/Okc77.png

You have the liberty to choose any name for the variable (like in the moment example).

If you're still confused, feel free to ask for clarification.

Answer 9

Answer №5

Simply follow these steps:

import dayjs, {Dayjs} from 'dayjs';

In your tsconfig.json, make sure to enable AllowSyntheticDefaultImports and set it to true starting from Typescript version 2.0 (it's already enabled by default).

Answer 10

Simply follow these steps:

import dayjs, {Dayjs} from 'dayjs';

In your tsconfig.json, make sure to enable AllowSyntheticDefaultImports and set it to true starting from Typescript version 2.0 (it's already enabled by default).

What is the best way to merge import all with different elements?

Answer №1

Answer №2

Answer №3

Answer №4

Answer №5

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