Why is the strict equality operator slightly slower than the equality operator in javascript?
As I have read from the accepted answer here, strict equality comparison should be slightly faster than normal equality, as it doesn't involve type coercion, quote
Strict comparison (===) will always be slightly faster, but the difference is usually negligible
However, when I tried to benchmark this in-browser, the result seems to suggest otherwise
I tried the following code, which runs both types of equality on the same two strings ("123456") for 10000 times and benchmarks their execution time.
console.time("test");for(i=0;i<10000;i++)if("123456"==="123456")continue;console.timeEnd("test");
console.time("test2");for(i=0;i<10000;i++)if("123456"=="123456")continue;console.timeEnd("test2");I got:
test: 0.342041015625 ms
test2: 0.26318359375 ms
which suggests that normal equality should be faster than strict equality in the context of strings. Benchmarking on numbers shows similar results
console.time("test");for(i=0;i<10000;i++)if(123456===123456)continue;console.timeEnd("test");
console.time("test2");for(i=0;i<10000;i++)if(123456==123456)continue;console.timeEnd("test2");output:
test: 0.4560546875 ms
test2: 0.316162109375 ms
why?
Answer
Because of JavaScript engine optimizations, especially in V8:
When both operands are known constants (like two literals), the engine can apply constant folding and dead code elimination, making both == and === extremely fast — sometimes even optimized away entirely.
The loose equality == skips the type check when both operands are already the same type, which can make it marginally faster than === in tight loops involving primitives.
However, the difference is negligible and only shows up in artificial micro-benchmarks.
In real-world usage, === is just as fast or faster, and should always be preferred unless coercion is explicitly needed.