javascript - variable - unexpected token import




es6-import all named module without alias (2)

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.

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

import * as name from "module-name";

Ref: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/import

Actually, I have re-exported my modules in A.js and the same is inherited in B.js. PFB. Now, it's two level of inheritance, so it's not a big deal to import the named modules. But, when I'm taking this to 5 level of inheritance (A -> B -> C -> D -> E), I need to import all named modules in all files and need to do the (re)export the same in all. Instead of doing this,

  • Is there any other way to copy scope of all named modules into all level without reiterating the wheel (Import and Export)
  • Behind the scene of this design is to make them to follow Opps concept and to avoid the redeclaration of the same modules.

A.js

import React from 'react';
import I18n from 'i18n-js';
import m1 from 'module1';
import m2 from 'module2';

export default class A extends React.Component {}

export {React, I18n, m1, m2)

B.js

import BaseComponent from './A';
import {React, I18n, m1, m2) from './A;

export default class B extends A {}

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


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 ;)





reactjs