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javascriptecmascript-6commonjs

ES2015 `import` alternative for `require()()`?

Some Node JS libraries (e.g. debug) use this pattern with require statements:

var debug = require('debug')('http');

This is basically a require of a function which is then directly invoked.

My question: Is there a similar construct using ES2015 import statements?

How would you translate such code if you were converting from commonjs to es2015 syntax?

Solution

  • That pattern only works because require(debug) returns a value that can be used immediately.

    var debug = require('debug')('http');

    import is a bit like if in the sense that it doesn't resolve as a value.

    var d = if(a) { b } else { c }; // unexpected token
var debug = import debug from 'debug'; // unexpected token

    require shares semantics with the ? operator which performs the same function as if, but resolves as a value.

    var d = a ? b : c;
var debug = require('debug');

    The only option is to split the statement up.

    import _debug from 'debug';
var debug = _debug('http');