Modules/Async/A
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< Modules(Redirected from Modules/require/async/A)
STATUS: PROPOSAL
- Implementations
- [[Implementations/Yabble|]]
This a proposal for the specification of the "require.ensure" method. (Formerly "require.async".)
Contract
- An "ensure" function is defined as a property of the value of the free variable "require" provided in the module scope. "require.ensure" accepts an array of module identifiers as first argument and a callback function as second argument.
- The callback function must be called as soon as all of the foreign modules, and their shallow and deep dependencies are available for synchronous require.
- The callback function must be passed the "require" function as its first argument.
Unspecified
This specification leaves the following important points of interoperability unspecified:
- the return value of "require.ensure" to allow for future modifications of the specification, notably the inclusion of promises,
- the means by which the foreign modules are loaded, and
- the presence of a timeout.
Sample Code
- math.js
exports.add = function() { var sum = 0, i = 0, args = arguments, l = args.length; while (i < l) { sum += args[i++]; } return sum; };
- increment.js
var add = require('math').add; exports.inc = function(val) { return add(val, 1); };
- program.js
require.ensure(['increment'], function(require) { var inc = require('increment').inc; var a = 1; inc(a); // 2 });
Notes
- Given the semantic shift this method has taken thanks to Wes Garland's suggestions, the name "require.async" no longer seemed appropriate. We ended up agreeing on "require.ensure" instead.
- This specification only defines "require.ensure" on the module scope's free variable "require". If a module loader also has a global variable "require", it MAY choose to mirror the ensure function on that object or function as well, but that is the module loader's prerogative.
Related Discussion
- Updated Transport proposals
- IRC log. Discussion starts at 00:34.