only use javascript

A frequency counter is an object (JavaScript), dictionary (Python), hash (Ruby) composed of key:value pairs where the each key is an element originating from some other data structure and the corresponding value is the amount of times, or frequency, that particular element appears. Task Write out a function, frequency Counter (word). For input, you will be given a string referenced as word. For output, you will return a boolean. Compose an object which is composed of the keys and values that reflect the letters found in word and the corresponding frequencies of those respective letters. Return true if all of the letters in word appear once and only once. Otherwise, return the false value