When selecting DOM elements in JavaScript, two common methods are document.querySelector()
and document.getElementById()
. But which one is faster and when should you use each? Let’s break it down. See Memory Management in JavaScript.
Benchmark tests consistently show that:
✅ getElementById()
is faster than querySelector()
.
getElementById()
directly accesses the DOM’s optimized ID lookup system.querySelector()
uses a CSS selector engine, which adds slight overhead.console.time('getElementById');
for (let i = 0; i < 10000; i++) {
document.getElementById('test');
}
console.timeEnd('getElementById'); // ~1-5ms
console.time('querySelector');
for (let i = 0; i < 10000; i++) {
document.querySelector('#test');
}
console.timeEnd('querySelector'); // ~5-15ms
Result: getElementById()
is 2-10x faster in most cases.
getElementById()
When:querySelector()
When:.class
, [attribute]
, parent > child
).Method | Speed | Use Case |
---|---|---|
getElementById() | ⚡ Fastest | Best for simple ID lookups. |
querySelector() | 🐢 Slower | Best for complex selectors. |
getElementById()
.querySelector()
.Pro Tip: For modern JS, getElementById()
is still king for pure performance—but querySelector()
is more versatile.
Which do you prefer? 🚀
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