CodeSOD: True Confession: Without a Map

Today, we have the special true confession from Bruce, who wrote some bad code, but at least knows it's bad.

Bruce is a C# developer. Bruce is not a web developer. Someone around the office, though, had read an article about how TypeScript was closer to "real" languages, like C#, and asked Bruce to do some TypeScript work.

Now, in C# parlance, your key/value pair data-structure is called a Dictionary. So, when Bruce got stuck on how to store key/value pairs in TypeScript, he googled "typescript dictionary", and got no useful results.

Disappointed, Bruce set out to remedy this absence:

export class KeyValuePair<TKey,TValue> { Key: TKey; Value: TValue; constructor (key: TKey, value: TValue) { this.Key = key; this.Value = value; }}export class Dictionary<TKey, TValue>{ private Collection: Array<KeyValuePair<TKey, TValue>> private IndexMap: Map<TKey, number> private index: number; public tryAdd(key: TKey, value: TValue): boolean { if (this.containsKey(key)) { return false; } else { var kv = new KeyValuePair(key, value); this.IndexMap.set(kv.Key, this.Collection.push(kv) - 1); return true; } } public tryRemove(key: TKey): boolean { var i = this.indexOf(key); if (i == -1) { return false; } else { this.Collection.splice(i, 1); this.reMap(i, key); return true; } } public indexOf(key: TKey): number { if (this.containsKey(key)) { return this.IndexMap.get(key); } else { return -1; } } public containsKey(key: TKey): boolean { if (this.IndexMap.has(key)) { return true; } else { return false; } } private reMap(index: number, key: TKey) { this.index = index; this.IndexMap.delete(key); this.IndexMap.forEach((value: number, key: TKey) => { if (value > this.index) { this.IndexMap.set(key, value - 1); } }); }//the rest is recreating C# dictionary methods: getKeys(),getValues(), clear(), etc.}

The dictionary implementation stores an array of key/value pairs. Now, it'd be expensive to have to search every item in the collection to find the appropriate key/value pair, so Bruce knew he needed to find a way to map keys to values. So he used a Map to store pairs of keys and indexes within the array.

He spent an entire afternoon coding this masterpiece before realizing that Maps stored key/value pairs" just like a dictionary.

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