Should I use require or import?

The use of require is very simple, it is equivalent to the portal of module.exports, what is behind module.exports, what is the result of require, objects, numbers, strings, functions... ...And then assign the result of require to a variable, which is equivalent to overlapping the positions of require and module.exports in parallel space.

And theoretically require can be used anywhere in the code, even without assigning a value to a variable before use, such as:

require('./a')(); // module a is a function, execute module a function immediately
var data = require('./a').data; // A module exports an object
var a = require('./a')[0]; // A module exports an array

When you use it, you can completely ignore the concept of modularity and use require, just treat it as a built-in global function of node, and its parameters can even be expressions:

require(process.cwd() + '/a');

But import is different, it is compiled at compile time (require is at runtime), it must be placed at the beginning of the file, and the format used is also definite, so there is no doubt. It does not assign the entire module to a variable after running, but only selects the import interface for compilation, which is much better in performance than require.

From the perspective of understanding, require is an assignment process, and import is a deconstruction process. Of course, require can also deconstruct the result and assign it to a set of variables, but when import encounters default, it is completely identical to require. Different:var $ = require('jquery'); with import $ from 'jquery'They are two completely different concepts.

There is no answer to the question "require or import instead?" because this question is currently unanswerable, because all engines have not yet implemented import. We Using babel in node to support ES6, it just transcodes ES6 to ES5 and then executes, the import syntax will be transcoded to require. This is why module.exports is used when exporting modules, and import is still effective when importing modules, because in essence, import will be transcoded to require for execution.

However, we must know this truth, ES7 will be released soon, and js engines will implement the ES6 standard as soon as possible. If an engine cannot even achieve the standard, it will be eliminated ,ES6 is a matter of time. If you are still deploying require in your code, you must upgrade your code when ES6 is supported by the engine, and if you start deploying import now, you may only need to do very few changes in the future.