es6 - import all named module without alias

Question

I know that we can import all named modules with alias as below,

import * as name from \"module-name\";

Ref: https://developer.mozilla.org

Answer 1

For Now, there is no clean way to do this. But you can overcome the problem by :

1) defining an alias

import * as foo from "foo"

2) writing all modules

import {a,b,c,d,...} from "foo"

Answer 2

global is your current scope in node.js, similar to the window object in the browser, so you can import into this object.

To import all symbols from util module:

import * as util from "./util";
util.importAll(util, global);

In util.js:

/**
 * Takes all functions/objects from |sourceScope|
 * and adds them to |targetScope|.
 */
function importAll(sourceScope, targetScope) {
  for (let name in sourceScope) {
    targetScope[name] = sourceScope[name];
  }
}

... and a number of other functions like assert() etc., which I need everywhere, and which should be part of the JavaScript language, but are not yet. But as others said, use this sparingly.

Answer 3

Is there any way to import all named modules without alias like import {*} from './A' (instead of 2nd in B.js)

No.

And the whole idea of re-exporting more than you need to save the "number of lines" in the final js file as you stated at

Bcz, It's putting two lines for each import in the final js file. Consider If there are 10 import lines than, 20 lines will be added in final js. When you are thinking for production it will too cost

Does not make much sense, since that's what JS minifiers are for.

To summarise: one should not do that at the very first place:

1. You export only what you need to export
2. You import whatever you need wherever you need.
3. You use JS minifiers to optimise the output JS file size.

Answer 4

JavaScript solution:

import * as exports from 'foo';
Object.entries(exports).forEach(([name, exported]) => window[name] = exported);

Note: the imported wrapper object remains there.

---

Node.js solution:

Object.entries(require('foo')).forEach(([name, exported]) => global[name] = exported);

Answer 5

Here's a crazy experiment I did, that works, but it's probably dangerous in ways I don't fully understand. Would somebody explain to me why we don't do this?

var lodash = require("lodash");

function $localizeAll(name) {
    return `eval("var " + Object.getOwnPropertyNames(${name}).reduce((code, prop)=>{
        if (/^[a-zA-Z$_][a-zA-Z$_0-9]*$/.test(prop)) {
            return code.concat(\`\${prop} = ${name}["\${prop}"]\n\`);
        } else {
            console.warn("did not import '" + prop + "'");
            return code;
        }
    }, []).join(", ")+";")`
}

// this will make all exports from lodash available
eval($localizeAll("lodash"));

console.log(add(indexOf([1,2,6,7,12], 6), 5)); // => 7

It's a bit complicated as it evals in two levels, but it basically iterates of all the properties of an object with the given name in scope and binds all properties that have names qualified to be identifiers to an identifier by that name:

var length = lodash["length"]
  , name = lodash["name"]
  , arguments = lodash["arguments"]
  , caller = lodash["caller"]
  , prototype = lodash["prototype"]
  , templateSettings = lodash["templateSettings"]
  , after = lodash["after"]
  , ary = lodash["ary"]
  , assign = lodash["assign"]
  , assignIn = lodash["assignIn"]
  , assignInWith = lodash["assignInWith"]
  , assignWith = lodash["assignWith"]
  , at = lodash["at"]
  , before = lodash["before"]
  , bind = lodash["bind"]
  , bindAll = lodash["bindAll"]
  , bindKey = lodash["bindKey"]
  //...
  , upperCase = lodash["upperCase"]
  , upperFirst = lodash["upperFirst"]
  , each = lodash["each"]
  , eachRight = lodash["eachRight"]
  , first = lodash["first"]
  , VERSION = lodash["VERSION"]
  , _ = lodash["_"]
  ;

There are some examples in this list of why this is a bad idea (e.g. it shadows arguments).

You should be able to use this as follows (though you probably shouldn't like they say above).

B.js

import BaseComponent, * as extras from './A';

eval($localizeAll("extras"));

export default class B extends BaseComponent {}

Anyways, couldn't resist trying this out ;)