Speed/cost of localStorage

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Just made a small benchmark. What i plan to do is to get some data from localStorage quite often and i wondered will it block. While localStorage.getItem is synced operation it may sound scary but is it?

  • 1st test to call 1 million times localStorage to get item which does exist.
  • 2nd test to call 1 million times localStorage to get item which does NOT exist.

Results:

“Item found: 0.0007991071428571318ms per call”

“Item not found: 0.0006365004639793477ms per call”

In short – just use it. It takes no time. 0.0007 of 1 millisecond.

 let results = [];
 let sum = 0;
 localStorage.setItem('foo', 'foo bar baz foo bar baz foo bar baz foo');

 for (let i = 0; i < 1000000; i++) {
   let a = performance.now();
   localStorage.getItem('foo');
   let result = performance.now() - a;
   sum += result;
   results.push(result);
 }

 console.log(`Item found: ${sum / results.length}ms per call`);

 results = [];
 sum = 0;
 for (let i = 0; i < 1000000; i++) {
   let a = performance.now();
   localStorage.getItem('bar');
   let result = performance.now() - a;
   sum += result;
   results.push(result);
 }

 console.log(`Item not found: ${sum / results.length}ms per call`);

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