There are many cases involving nested data structures where the ability to
define a default value in Maps would be helpful.
Straw Man:
var map = new Map(=> [])
var arr = map.get('foo')
arr === map.get('foo') // true
This enables:
map.get('foo').push(obj)
Which would be (*very*) approximately equivalent to:
class MapWithDefault extends Map {
constructor(default) {
this.defaultValue = default;
super();
}
get(key) {
if (!this.contains('foo')) {
let value = this.defaultValue(key);
map.set(key, value);
}
return super(key);
}
}
--
Yehuda Katz
(ph) 718.877.1325
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