Walmart customers are furious after the retailer ran out of Black Friday sale items despite a huge online investment (WMT, AMZN)

Customers are slamming
Walmart kicked off its online Black Friday sale at 12:01 a.m. on Thanksgiving Day.
The retailer has tripled its online assortment for the holiday season this year — but it will need to keep items in stock if it wants to compete with Amazon.

Some customers are furious at Walmart after the retailer ran out of Black Friday sales items on Thanksgiving Day.

"What's the point in having online black Friday if everything is either out of stock or in store purchase only?" says one comment posted on Walmart's Facebook page on Thursday.

Another says: "Why is it that many of the sale items in the black Friday ad that are supposed to be available all day today are not online?!?! This is ridiculous and the worst crap walmart has pulled yet!"

"Nothing is in stock online and store selection sucks," says a third.

Walmart's Black Friday sales started online at midnight on Thursday. By Thursday evening, many of the items had sold out.

Items that were out of stock included electronics like as the advertised Sharp Smart LED TV, video games, and best-selling clothing like Wrangler jeans, kids' pajamas, and fleece jackets.

Several people are also saying that they ordered items from Walmart early on Thursday morning to be told later in the day that the items had sold out and that they would not receive them.

As of Friday morning, Walmart seemed to have restocked some items. The Sharp Smart LED TV, for example, was sold out on Thursday evening but showed seven were in stock at about 8:45 a.m. on Friday.

Walmart did not immediately respond to Business Insider's request for comment.

In any case, restocking later doesn't prevent customers' anger now — or help Walmart compete with Amazon.

Walmart made a major investment in its online shopping business this year, adding perks like free two-day shipping on orders of more than $35. The retailer announced earlier this month that it had tripled its online assortment, including doubling its toy offerings, for the holidays from a year ago.

Keeping these items in stock online is crucial for Walmart if it wants to compete with Amazon. While Amazon's prices sometimes skyrocket on uber-popular items, the e-commerce giant rarely runs out of stock, thanks to the extensive range of third-party retailers also selling them on the site.

Fingerlings, for example, quickly sold out on Walmart.com on Thanksgiving at the price of $14.48. Meanwhile, on Amazon, the toy is selling for more than $50 from a number of third-party sellers.