I'm reading some codes and I realized that always after this a comma and added, I've never seen anything like that. Why use the comma, and is this comma just for readability?

I usually do it this way:

var break__ = Breakpoints_.prototype;
break__.initialize = function () {
    this._breakpoint = null;
    this._lastBreakpoint = null;
    this._handleOldIE();
    this._breakpointOrder = this._setBreakpointOrder();
    this._isOldIE || this._handleResize();
}

And I'm noticing some codes like this:

var break__ = Breakpoints_.prototype;
break__.initialize = function () {
    this._breakpoint = null,
        this._lastBreakpoint = null,
        this._handleOldIE(),
        this._breakpointOrder = this._setBreakpointOrder(),
        this._isOldIE || this._handleResize()
}

Should I use commas or semicolons? and what is the function of these commas?