Code points

[AlgoTrader]

Most of JS code is overengineering and bad JS style.

Examples are

Map.prototype._escapeKey = function (key) {
    return '$' + key;
};

just write

function escape(key) {
    return '$' + key;
};

Never make _stuff to make private node.js module funcations

The other example

Map.prototype.get = function (key) {
    return this.has(key) ? this._values[this._escapeKey(key)] : undefined;
};

The same is:

Map.prototype.get = function (key) {
    return this._values[escapeKey(key)];
};

JS is a beatiful language when used properly, please don't write shit code.
I think your JS/node knowledge is poor

[jsymfony]

1. Making variables and methods prefixed with underscore indicates that they should not be accessed directly. It's done only to increase abstraction
2. Also naming method escapeKey indicates that this function returns escaped Key, not escaped prisoner.
3. Using notation with "has" allows to easily modify "has" logic later without changing other piece of code.

Read about abstraction in programming. Protected and private methods exists generally to split interface methods and some internal methods to prevent incorrect usage of internal methods