这些ES6导入方法有什么区别？ [英] What is the difference between these ES6 import methods?

问题描述

这些导入方法有什么区别？

What is the difference between these import methods?

方法1：

import {sum, pi} from "lib/math";

方法2：

import exp, {pi, e} from "lib/mathplusplus";

es2015文档显示了这两个示例，我无法弄清花括号的目的。似乎所有导入后列出的东西都将被分配给窗口对象。

The es2015 docs showed these two examples, and I can't figure out the purpose of the curly braces. It seems like all of the things listed after import will be assigned to the window object anyway.

文档供参考： https://babeljs.io/docs/learn-es2015/

推荐答案

模块可以导出多个东西。模块也可以有一个默认导出。

modules can export multiple things. Modules can also have a single "default" export.

从somelib导入exp;

将 somelib 的默认导出分配给变量 exp 。

This assigns the default export of somelib to the variable exp.

从somelib导入{a，b};

这将非默认命名导出 a 和 b 分配给局部变量 a 和 b 。

This assigns the non-default named exports a and b to local variables a and b.

import exp，{a，b} fromsomelib;

将默认导出分配给 exp 和命名导出到 a 和 b 。

import * as somelib fromsomelib;

并将它们作为对象分配给局部变量 somelib ，这意味着您将具有 somelib.a ， somelib.b 等。

Takes all of the named exports of somelib and assigns them as an object to the local variable somelib, which means you will have somelib.a, somelib.b, etc.

这是一个非常好的资源： http://www.2ality.com/2014/09/es6-modules-final.html

This is a very good resource for the topic: http://www.2ality.com/2014/09/es6-modules-final.html

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