Recommended Free Tools
For an array you already know is an array, check whether its length is greater than zero: items.length > 0. This tests whether the array contains at least one element—not whether any element is truthy.
Check whether a known array has elements
Use items.length > 0 for a non-empty branch, or items.length === 0 for an empty branch:
const items = ["keyboard", "mouse"];
if (items.length > 0) {
console.log("The array has at least one element.");
}
if (items.length === 0) {
console.log("The array is empty.");
}These checks ask whether the array has any elements. They do not inspect what those elements contain.
Handle arrays that may be null or undefined
If an array reference might be missing, check for that before reading length. With TypeScript’s strictNullChecks, null and undefined are separate types, so TypeScript requires you to narrow them before accessing array properties. The TypeScript handbook explains strictness and null checking.
#1 Best Overall
- Read Before You Buy — No Video Output: These adapters support charging and USB 2.0 data transfer, but cannot transmit video signals. Except for standard USB webcams (which use USB data only), they are not compatible with HDMI/DisplayPort cables, video-capable USB-C hubs, or docking stations with video output.
- Convert USB-A Ports to USB-C: Designed to connect USB-C earphones, cables, flash drives, card readers, and other USB-C accessories to standard USB-A ports. Plug-and-play with no drivers or software required.
- Aluminum Alloy Housing: Built with a sturdy aluminum alloy shell that aids in heat dissipation and protects against daily wear and scratches. Designed to maintain a stable and secure connection.
- Compact & Travel-Friendly: The ultra-compact design allows the adapter to stay plugged into your device without blocking adjacent ports or adding bulk, reducing wear and tear on your original USB ports.
- 12-Month Warranty: Backed by a 12-month manufacturer warranty for peace of mind. Designed to meet strict quality control standards for reliable everyday performance.
Use an explicit nullish check
if (items && items.length > 0) {
// items is present and non-empty
}Treat missing and empty as the same outcome
Optional chaining and nullish coalescing let you write a compact check that returns false when items is either null or undefined:
const hasItems = (items?.length ?? 0) > 0;Use this when a missing array and a present-but-empty array should both mean “no items.” If your application needs to tell those cases apart, check for null or undefined separately.
Rank #2
- 5-in-1 USB-C Hub: Experience comprehensive connectivity featuring a Power Delivery input, two USB-A 2.0 ports, a USB-A 3.0 port, and an HDMI port. (Note: The USB-C power delivery input port is only for connecting an external wall charger to power your laptop and cannot power peripheral devices.)
- 90W Pass-Through Charging: Achieve optimal charging with 90W pass-through power to your laptop, supported by a total input of 100W, with the hub reserving 10W for operational efficiency. (Note: Wall charger not included.)
- Quick Data Transfers: Accelerate your productivity with rapid data transfers using a high-speed 5Gbps USB 3.0 port and two 480Mbps USB 2.0 ports.
- 4K HDMI Display: Enhance your visual experience with a hub capable of delivering 4K resolution at 30Hz in both mirror and extend modes. Please note that this hub is compatible with MacBook (macOS 12 and newer), Windows 10 and 11, ChromeOS, and laptops equipped with DP Alt Mode and Power Delivery. Note: This device is not compatible with Linux.
- What You Get: Anker USB-C Hub (5-in-1, 4K HDMI), welcome guide, 18-month warranty, and our friendly customer service.
Choose the check that matches the input
| Input or goal | Check | Result |
|---|---|---|
| Known array; test for elements | items.length > 0 |
True when at least one element exists. |
| Known array; test for emptiness | items.length === 0 |
True when the array has no elements. |
| Nullable array; missing and empty both mean no items | (items?.length ?? 0) > 0 |
True only when the array is present and has positive length. |
| Unknown runtime value | Array.isArray(value) && value.length > 0 |
True only when the value is an array with at least one element. |
Why not use if (items) or compare with []?
Arrays are objects, and even an empty array is truthy in JavaScript. So if (items) checks that the reference is truthy; it does not establish that the array has elements.
Likewise, items === [] is not an emptiness check. Equality compares object identity, and each [] literal creates a new array. Use items.length === 0 instead. The TypeScript 4.8 release notes call out array-literal equality as a foot-gun.
Windows Errors? Fix Them Before They Spread
Repair common Windows errors and clear accumulated junk for a smoother, more stable PC - no reinstall needed.Free scan · no reinstallCrashes, No Sound, or Screen Glitches?
Random freezes, missing sound and display glitches usually trace back to one bad driver. Find and replace yours safely.Free scan · under a minuteRank #3
- Sleek 7-in-1 USB-C Hub: Features an HDMI port, two USB-A 3.0 ports, and a USB-C data port, each providing 5Gbps transfer speeds. It also includes a USB-C PD input port for charging up to 100W and dual SD and TF card slots, all in a compact design.
- Flawless 4K@60Hz Video with HDMI: Delivers exceptional clarity and smoothness with its 4K@60Hz HDMI port, making it ideal for high-definition presentations and entertainment. (Note: Only the HDMI port supports video projection; the USB-C port is for data transfer only.)
- Double Up on Efficiency: The two USB-A 3.0 ports and a USB-C port support a fast 5Gbps data rate, significantly boosting your transfer speeds and improving productivity.
- Fast and Reliable 85W Charging: Offers high-capacity, speedy charging for laptops up to 85W, so you spend less time tethered to an outlet and more time being productive.
- What You Get: Anker USB-C Hub (7-in-1), welcome guide, 18-month warranty, and our friendly customer service.
Check array occupancy separately from element values
A positive length means at least one element is present, even if that element is falsy: [0], [false], and [""] are all non-empty arrays.
If your actual requirement is “at least one usable element,” define what makes an element usable and test that condition explicitly. For example, use item !== undefined when zero is valid but undefined is not. A truthiness filter can wrongly discard zero when the intended test is specifically for undefined; this distinction is discussed in the TypeScript 5.5 release notes.
Rank #4
- Dual Converters, Infinite Potential：Includes 2× USB C male to USB A female adapters and 2× USB A male to USB C female adapters. Perfect for a wide range of uses—tablets with Bluetooth keyboards, expand USB ports on macbook, and more. Two different converters for all your daily needs
- Next-Level 10Gbps & 3A Charging: No more slow 480Mbps, this usb to usb c adapter has a transfer speed of up to 10Gbps, allowing you to do more transferring in less time. This usb adapter fits both USB A and USB C charger, supporting up to 3A fast charging
- Upgraded Exquisite Craftsmanship: With an aluminum alloy housing and metal connector, the usbc to usb adapter is extremely durable and sturdy. Rigorously tested to withstand more than 10,000 times of plugging and unplugging, ensuring long-lasting performance
- Broad Compatible: The usb c to usb adapter widely supports all USB C/ USB A devices like laptops, tablets, cellphones, car chargers, and phone chargers. Such as compatible with MacBook Pro/Air 2023/2022, Thunderbolt 4/3 Devices,Apple MagSafe Watch 9/8/7/SE/Ultra, iPad Pro 2022/2021, Samsung Galaxy S23/S20/S10, and iPhone 17/16/15 Pro. Plug and play
- Please Note: To reach 10Gbps speed, keep the cable under 3.3 ft. For USB A Male to USB C adapters, try flipping the USB C connector. USB C Male to USB A adapters support bidirectional 10Gbps transfer within 3.3 ft
Validate unknown input before checking its length
For values from untrusted runtime input or typed as unknown, confirm the value is an array before reading length. The TypeScript handbook’s narrowing guidance identifies Array.isArray as the runtime array check.
function hasItems(value: unknown): boolean {
return Array.isArray(value) && value.length > 0;
}The first condition narrows the value to an array; the second checks whether that array has any elements.
Quick Recap
Best Value
- 5-in-1 Connectivity: Equipped with a 4K HDMI port, a 5 Gbps USB-C data port, two 5 Gbps USB-A ports, and a USB C 100W PD-IN port. Note: The USB C 100W PD-IN port supports only charging and does not support data transfer devices such as headphones or speakers.
- Powerful Pass-Through Charging: Supports up to 85W pass-through charging so you can power up your laptop while you use the hub. Note: Pass-through charging requires a charger (not included). Note: To achieve full power for iPad, we recommend using a 45W wall charger.
- Transfer Files in Seconds: Move files to and from your laptop at speeds of up to 5 Gbps via the USB-C and USB-A data ports. Note: The USB C 5Gbps Data port does not support video output.
- HD Display: Connect to the HDMI port to stream or mirror content to an external monitor in resolutions of up to 4K@30Hz. Note: The USB-C ports do not support video output.
- What You Get: Anker 332 USB-C Hub (5-in-1), welcome guide, our worry-free 18-month warranty, and friendly customer service.
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
