Array.includes对比多条件if语句是否存在性能负面影响？

Great question! I’ve swapped out those clunky multi-condition if statements for Array.includes too—cleaner code is always a win, but it’s smart to check the tradeoffs. Let’s break this down:

Performance Impact #

First, the big one: for most everyday code, the performance difference is negligible. Modern JavaScript engines (V8, SpiderMonkey, etc.) optimize includes really well, so you won’t notice a slowdown unless you’re dealing with extreme scenarios:

• High-frequency loops: If you’re running this check millions of times in a tight loop, includes (which does a linear scan of the array, O(n)) will be slower than a chain of === checks (O(1), since it stops at the first true condition). For example, checking against an array of 1000 elements in a loop would add up, but this is rare in typical business logic.
• Small arrays: For arrays of 3-5 elements like your example, the engine can often optimize the scan to be almost as fast as hardcoded || checks.

Pro tip: If you’re reusing the same allowed values multiple times, extract the array to a constant outside the check to avoid recreating it every time:

// Better: Reuse the array
const allowedValues = ['b', 'c', 'd'];
if (allowedValues.includes(variable)) {
  // ...
}

Technical Drawbacks to Watch For #

While includes is great, there are a few edge cases to keep in mind:

• NaN handling: includes uses the SameValueZero comparison, which means [NaN].includes(NaN) returns true, whereas NaN === NaN is false. If your logic relies on treating NaN as "not equal to itself," this will change behavior.
• Type consistency: Like ===, includes doesn’t do type coercion. So ['1'].includes(1) is false, same as 1 === '1'—this is consistent, but worth confirming if you’re coming from loose equality habits.
• Long arrays hurt readability and performance: If you’re checking against 10+ values, an array can get unwieldy. In that case, using an object or Set might be better:

  // Faster lookups for large sets, and cleaner to read
  const allowedSet = new Set(['b', 'c', 'd', /* ... 10 more values ... */]);
  if (allowedSet.has(variable)) {
    // ...
  }
  

  Set.has() is O(1), just like object property checks, so it’s faster for large collections.

When to Stick with Array.includes #

• Your condition list is short (3-5 values): The code is far more readable than a messy chain of || checks.
• You need dynamic conditions: If the allowed values change at runtime (e.g., fetched from an API), building an array and using includes is way easier than dynamically generating a string of === checks.
• Readability is your top priority: In most apps, maintaining clean, understandable code beats micro-optimizations that no user will ever notice.

Final Verdict #

For 99% of use cases, Array.includes is a fantastic replacement for multi-condition if statements. The performance hit is negligible in everyday code, and the cleaner syntax is worth it. Only worry about alternatives if you’re in a performance-critical loop with large datasets, or if you need to preserve the exact behavior of NaN === NaN.

内容的提问来源于stack exchange，提问作者Christian