Package Exports

defaultdict2

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Readme

defaultdict

Returns a new dictionary-like object

Behaves exactly like Python's defaultdict.

defaultdict(default_factory, initial_dict)

default_factory: value or function to be used for missing keys initial_dict: (optional) dictionary to start with

Getting started

The first argument is the value for missing keys - it can be a value or function like in Python.

var p = defaultdict(0);
p.a++; 
p.b++;
console.log(p);
// { a: 1, b: 1 }

Same example using a function:

var p = defaultdict(()=>0);
p.a++; 
p.b++;
console.log(p);
// { a: 1, b: 1 }

The function will be called with two arguments target_dict,name.

Initial dictionary

You can add an initial dictionary as second argument.

var p = defaultdict(0, {a: 1});
p.b++;
console.log(p);
// { a: 1, b: 1 }

Nested dictionaries

There is no limit to your creativity!

var p = defaultdict(()=>defaultdict(0));
p.a.b++;
console.log(p);
// { a: { b: 1 } }

Gotchas

Javascript doesn't allow string keys on dictionaries -> h[20] will create the key '20'

var p = defaultdict(0, {1: 1});
console.log(1 in p);
// false
console.log('1' in p);
// true

Be careful when checking for existence. Either use in or set the d.default_factory to undefined

var p = defaultdict(0, {a: 1});
console.log('b' in p);
// false
p.default_factory = undefined;
console.log(p.b);
// undefined

Requirements

This depends on ES6 proxies. They should be part of your node version.