The FAANGs are back in fashion.

As markets have rebounded from December doldrums, the FAANG gang has also returned with a vengeance. The S&P 500 and Nasdaq indices closed at all-time highs on Tuesday, at 2,933 and 8,109.69 respectively.

That means for 2018 is ancient history for now, with each of the FAANG names notching substantial gains so far this year. Netflix (NFLX - Get Report) has added the most value of the group, with shares up about 40% year-to-date, while Alphabet (GOOGL - Get Report) has added the least at 18.8%.

That's a far cry from the back half of last year, when factors ranging from Facebook's (FB - Get Report) parade of terrible news to trade tensions were dragging down the market-leading FAANGs and leading investors to give some of their sky-high valuations a second look. As of Tuesday, the stock grouping had a combined value of roughly $3.5 trillion.  

Investment professionals describe a return to the mentality that dominated the earlier part of 2018, during which time the FAANG group saw gains that dominated stock indices. 

"The bigger picture is that growth has re-emerged as the most dominant area of the market; I think it's kind of a return to the environment that existed before," said Carlos Dominguez, chief investment officer at Element Pointe Advisors. "Investors are in that 'risk-on' mentality."

Needless to say, not all FAANGs are created equal -- they each have their idiosyncrasies, and in some cases have little in common other than their high valuations.

Apple (AAPL - Get Report) , for instance, was weighed down in part by uncertainty in U.S.-China relations, while Facebook was dogged by nonstop privacy scandals and heavier spending on related issues. The FAANG grouping also includes e-commerce and cloud giant Amazon (AMZN - Get Report) .

On the whole, however, their growth patterns are relatively insulated from certain macroeconomic events that could clobber other stocks in sectors such as manufacturing.

"One of the reasons that these stocks are trading well is that with the exception of Apple, none of them are exposed to a lot of trade problems...and on the margin, that's a benefit," Dominguez said.

A connection to U.S. economic growth is another factor that underpins sentiment around the FAANG names, added Tom Kennedy, head trader at New England Investment & Retirement Group.

According to Kennedy, better-than-expected GDP growth so far in 2019 has meant that the group bounced back harder. But their dominant status also means they aren't dependent on U.S. economic results. 

"Although they would be hurt by slower economic growth, they'll still remain growth stories despite any headwinds the U.S. would face," Kennedy said.

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