The first method we will implement is the hasKey(key) method. We will implement this method first because it will be used in other methods, such as set and remove. We can see its code as follows:
hasKey(key) { return this.table[this.toStrFn(key)] != null;}
JavaScript only allows us to use strings as the key/property of objects. In case we have a complex object passed as a key, we will need to transform it into a string. For this reason, we will always invoke the toStrFn function. In case there is a value pair for the given key (a position in the table not null or undefined), then we return true, otherwise, we return false.
