define

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2023-12-01

Create a new constructor function for a type inheriting from Sequence.

Signature

Sequence.define = function(methodName, overrides) { /*...*/ }

Sequence.define = function define(methodName, overrides) {
  if (!overrides || (!overrides.getIterator && !overrides.each)) {
throw new Error("A custom sequence must implement *at least* getIterator or each!");
  }

  return defineSequenceType(Sequence, methodName, overrides);
}

Name	Type(s)	Description
methodName	string\|Array.<string>	The name(s) of the method(s) to be used for constructing the new sequence. The method will be attached to the `Sequence` prototype so that it can be chained with any other sequence methods, like #map, #filter, etc.
overrides	Object	An object containing function overrides for this new sequence type. Must include either `getIterator` or `each` (or both). May include an `init` method as well. For these overrides, `this` will be the new sequence, and `this.parent` will be the base sequence from which the new sequence was constructed.
returns	Function	A constructor for a new type inheriting from `Sequence`.

Examples

// This sequence type logs every element to the specified logger as it
// iterates over it.
Lazy.Sequence.define("verbose", {
  init: function(logger) {
this.logger = logger;
  },

  each: function(fn) {
var logger = this.logger;
return this.parent.each(function(e, i) {
  logger(e);
  return fn(e, i);
});
  }
});

Lazy([1, 2, 3]).verbose(logger).each(Lazy.noop) // calls logger 3 times