There are dozens of stocks that have more than doubled this year, and it wouldn't be a surprise to see most of them take a breather in 2018. Triple-digit-percentage stock gains often exceed the improvement in their fundamentals, making a correction a logical if not healthy development. 

It doesn't have to be that way. Some of this year's biggest winners will keep piling on the gains in the year ahead. Square (SQ 0.51%), Shopify (SHOP 1.03%), and Weight Watchers (WW 14.10%) are three names that could very well keep the good times going in 2018.

Someone on a laptop checking out the Weight Watchers online management tool.

Image source: Weight Watchers.

Square -- Up 171%

There's no denying that the recent sizzle in the shares of the financial transactions specialist was the result of last month's move to let some of its more active Square Cash app users buy and sell bitcoins. If tiny companies tethering themselves to the cryptocurrency and blockchain dreams are taking off, why wouldn't an established player with a legitimate bitcoin story follow suit?

Thankfully for Square investors, the rally in the shares started well before the recent cryptocurrency fervor. The stock had already doubled by July, long before the bitcoin hype. Investors are buying into the platform's growing popularity. Square recently boosted its full-year adjusted revenue guidance, now targeting roughly 40% top-line growth. The bottom line has also started to clean up nicely. Square has beaten Wall Street profit targets with ease over the past four quarters, and analysts see explosive earnings growth in 2018. 

Square is well-positioned as the leading mobile point-of-sale platform for small- and mid-sized merchants in a corporate climate that's shining kindly on budding enterprises. Healthy growth and expanding margins should keep the cash coming in the year ahead.

Shopify -- Up 147%

Another company that had a monster 2017 by making life easier for small merchants is Shopify. The provide of online storefronts and other e-commerce solutions is growing quickly, with revenue soaring 72% in its latest quarter. A whopping $6.4 billion in transactions was generated through the Shopify platform, a year-over-year spike of 69%. 

It hasn't all been smooth sailing for Shopify this year. Noted boo bird Citron Research recently skewered Shopify's business model and valuation. Shopify has defended the promotional language of its referral network as legal and stands by the number of sites on its platform. The market eventually rewards growth, and as merchants continue hopping on Shopify to fortify their digital storefronts, the stock should continue to follow its fundamentals higher.

Weight Watchers -- Up 300%

Let's go low-tech for our third and biggest winner. Weight Watchers is the iconic weight-management platform that's been around for decades, becoming a growth darling in 2016 when Oprah Winfrey became a stakeholder and spokesperson. The stock gave back most of the initial post-Winfrey pop after Weight Watchers didn't experience an immediate jump in subscriptions, but the game has changed in 2017. 

Weight Watchers keeps growing as 2017 plays out, bumping its guidance sharply higher along the way. The stock has quadrupled, but that didn't stop B. Riley FBR analyst Kara Anderson from initiating coverage on Wednesday morning with a buy rating and an ambitious $65 price target. She sees many long-term growth levers that can keep moving the stock higher ahead of the upcoming 2018 "diet season" fueled by new year's resolutions.