是否建议使用===或!==？二元取值变量判等的性能差异

Great questions—these are exactly the kinds of details that help write robust, maintainable JavaScript. Let’s unpack each part one by one:

Absolutely—=== and !== are strongly recommended as the default choice for equality checks in JavaScript. Here’s why:

• The loose equality operators (==/!=) perform automatic type coercion, which can lead to unexpected, hard-to-debug results. For example:
  • 0 == false returns true
  • '' == false also returns true
  • null == undefined returns true
    These might seem intuitive at first, but they can create logic bugs when you’re expecting strict value-and-type matches.
• Strict equality checks explicitly compare both the value and the type of the operands, leaving no room for ambiguity. This makes your code’s intent crystal clear to other developers (and future you!). It’s the widely accepted best practice in the JS community for most scenarios.

Yes, it’s not just reasonable—it’s often the smarter choice, even with a limited set of possible values. Let’s say your variable can only be true or false, or 'active' or 'inactive':

• Using === ensures that even if something unexpected happens (like a bug that sets the variable to 0 instead of false, or '' instead of 'inactive'), your equality check won’t incorrectly match. This adds a small layer of defensive coding that can prevent subtle bugs.
• It also improves readability: when someone sees if (status === 'active'), they instantly know you’re checking for an exact string match, not just a value that coerces to the same result. There’s no guesswork involved.

Let’s cut to the chase: any performance difference between the two is negligible in real-world applications. Modern JavaScript engines (like V8 in Chrome/Node.js) are highly optimized, and the type coercion step for == adds barely any overhead.

That said, if we’re splitting hairs, === might be slightly faster in some cases because it skips the type coercion logic. But this difference is so tiny that it will never be the bottleneck in your code. Focus on writing correct, readable code first—optimize for performance only when you’ve identified a specific, measurable issue.

内容的提问来源于stack exchange，提问作者user9009597