stealjs / steal-conditional

Conditional loading

steal-conditional

Installation

Install the npm package running:

npm install steal-conditional --save-dev

then, add the extension to your package.json configDependencies so steal loads it before any application module

"system": {
  "configDependencies": [
    "./node_modules/steal-conditional/conditional"
  ]
}

Conditions Extension

Allows a condition module to alter the resolution of an import via syntax:

import $ from 'jquery/#{browser}';

Will first load the module 'browser' via System.import('browser') and take the default export of that module. If the default export is not a string, an error is thrown.

We then substitute the string into the require to get the conditional resolution enabling environment-specific variations like:

import $ from 'jquery/ie'
import $ from 'jquery/firefox'
import $ from 'jquery/chrome'
import $ from 'jquery/safari'

It can be useful for a condition module to define multiple conditions. This can be done via the . modifier to specify a member expression:

import 'jquery/#{browser.grade}'

Where the grade export of the browser module is taken for substitution.

Note that / and a leading . are not permitted within conditional modules so that this syntax can be well-defined.

Boolean Conditionals

For polyfill modules, that are used as imports but have no module value, a binary conditional allows a module not to be loaded at all if not needed:

import 'es5-shim#?conditions.needs-es5shim'

These conditions can also be negated via:

import 'es5-shim#?~conditions.supports-es5'

License

MIT