More stuff to buy on Walmart.com, more sales. Pretty simple equation. 

But perhaps an equation that Wall Street hasn't fully appreciated just yet. Walmart (WMT) - Get Report said on Thursday that its online sales surged 63% from the prior year as it significantly increased the number of items for sale, slashed prices and ventured into digital grocery ordering. Cowen analyst Oliver Chen estimates Walmart had 50 million items for sale on its website in the first quarter, up from 10 million a year ago. 

"Our take is that Walmart's commitment to value pricing is driving traffic and growth in grocery, and aggressive online strides are impacting same-store sales," Chen said.

Walmart's online sales growth stood out in what was a pretty decent quarter.  

Before Thursday's market open, the world's largest retailer reported first-quarter earnings of $1 a share on revenue of $118.8 billion. Wall Street expected earnings of 96 cents a share on sales of $117.8 billion.

The company's U.S. same-store sales rose 1.4%, held back by consumers delaying spending due to late tax refunds. Even still, Walmart's U.S. business outperformed that of its closest rival Target (TGT) - Get Report

Walmart shares rose 3.2% to $77.54 in Thursday trading. 

The first quarter caps a flurry of activity for Walmart's e-commerce operations. In April, Walmart started offering online customers the option of having their purchases sent to a local store instead of to their homes at a discounted shipping price. Digital ordering of groceries is now available at 670 Walmart U.S. stores. 

Meanwhile, Walmart's new e-commerce head Marc Lore, who founded Jet.com, continues to buy up e-commerce retailers that could help take on Amazon (AMZN) - Get Report .

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Editor's Pick: Originally published May 18.