Both require and import are used to import modules.

Import is the grammar standard in es6, and its corresponding is export;

And require is just a private global method of node, based on the AMD specification, corresponding to exports. Node.js is based on the CommonJS specification. AMD is very similar to CommonJS in its use.

Module loading time is different:

Require is runtime loading, and import is compiled at compile time. Therefore, require can be written anywhere in the code, and import needs to be written at the very top of the file.

The essence of the module:

requireIs the assignment process, it is equivalentmodule.exportsThe portal, what is the content behind module.exports, what is the result of require, objects, numbers, strings, functions... then assign the result of require to a variable.

The method of use is as follows:

Module output:
a.js:
module.exports={
    a:function(){
      ......
    },
 Url: "I am a bunch of links"
}
 Module import:
b.js:
var obj = require('./a);
obj.a();
console.log(obj.url);

If you need to use the require to load the es6 default export (export default mycomponent) module, you need to use require ('...').default。The main reason is: when processing the es6 module in node, the format of the module that is loaded and exported is:

{
 default:mycomponent
}

importIs a deconstruction process, the module of ES6 is not an object, but aexport The code that the command outputs. We use babel to support ES6 in node, and only transcode ES6 to ES5 and execute it. Now we use import in node and will be transcoded into require.

With import, you need to know about export.

export Statements are used to derive functions, objects, or raw values ​​from a module so that other programs can use them through the import statement.

The exported modules are in strict mode regardless of whether strict mode is declared.

There are two different export methods, named export and default export. Multiple named exports can be defined in each module, but only one default export is allowed.

Named export: Use the same name when importing.

In a.js:
 / / Export the method declared before
export { myFunction }; 

 // Export a constant
 Export const foo = Math.sqrt(9);//returns the square root of a number


 //Import in other scripts:
 In b.js:
import {myFunction,foo} from "./a";
console.log(myFunction());
 Console.log(foo);//output 3

Default export: When importing the default export, the import name does not need to match the name at the time of export.

In a.js:
 / / Export function
export default function() {}
 / / Export class
export default class A{......}
 Note: The above two default exports cannot appear in one file at the same time.

 Import in b.js:
import funM from './a';
import A from './a';

 

Note that you cannot usevar、letOrconstUsed to export default valuesexport default。

Therefore, to export a variable, write as follows:

Var a=1;//Declare the variable first

export default a;

The following way of writing is wrong: export default var a=1.

Essentially, the export default of the a.js file outputs a variable called default, and the system allows you to take any name for it.

So, about export default:

export default function (){}

 Equivalent to: 

var function a(){...}

export {a as default}

When importing:

import a from './x';
 Equivalent to:
import {default as a} from './x';