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Import a module lazily
JavaScript TypeScript
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fabiospampinato and sindresorhus Mention usage with bundlers in the readme (#16)
Co-authored-by: Sindre Sorhus <sindresorhus@gmail.com>
Latest commit 4fea4ed Jun 10, 2019

readme.md

import-lazy Build Status

Import a module lazily

Install

$ npm install import-lazy

Usage

// Pass in `require` or a custom import function
const importLazy = require('import-lazy')(require);
const _ = importLazy('lodash');

// Instead of referring to its exported properties directly…
_.isNumber(2);

// …it's cached on consecutive calls
_.isNumber('unicorn');

// Works out of the box for functions and regular properties
const stuff = importLazy('./math-lib');
console.log(stuff.sum(1, 2)); // => 3
console.log(stuff.PHI); // => 1.618033

Note

Destructuring will cause it to fetch eagerly

While you may be tempted to do leverage destructuring, like this:

const {isNumber, isString} = importLazy('lodash');

Note that this will cause immediate property access, negating the lazy loading, and is equivalent to:

import {isNumber, isString} from 'lodash';

Usage with bundlers

If you're using a bundler, like Webpack, you'll have to import your modules like this in order to have them properly bundled:

const importLazy = require('import-lazy');

const _ = importLazy(() => require('lodash'))();

Related

  • resolve-from - Resolve the path of a module from a given path
  • import-from - Import a module from a given path
  • resolve-pkg - Resolve the path of a package regardless of it having an entry point
  • lazy-value - Create a lazily evaluated value
  • define-lazy-prop - Define a lazily evaluated property on an object

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