Discussion on: You should stop using `parseInt()`

[lionel-rowe]

there are of course use cases where it’s beneficial to use it, for example if you want to extrapolate an integer out of a floating number, which is a good 50% faster than Math.round().

Two things here -

1. parseInt doesn't do any rounding, only truncation. The equivalent Math function would be Math.trunc:
   

   Math.round('0.999') // 1
   Math.trunc('0.999') // 0
   parseInt('0.999')   // 0
   
   Math.round('-0.999') // -1
   Math.trunc('-0.999') // -0
   parseInt('-0.999')   // -0
   

2. Running benchmarks in Chrome, the performance benefit of parseInt over Math.round is reversed if you explicitly convert to a number first:
   

   const bench = (desc, cb) => {
       const start = new Date()
   
       for (let i = 0; i < 1e7; ++i) {
           cb()
       }
   
       const end = new Date()
   
       console.log(desc, `${end - start} ms`)
   }
   
   bench('parseInt',       () => parseInt('3.2', 10))       // 374 ms
   bench('round coerced',  () => Math.round('3.2'))         // 738 ms
   bench('round explicit', () => Math.round(Number('3.2'))) //  70 ms
   bench('trunc coerced',  () => Math.trunc('3.2'))         // 671 ms
   bench('trunc explicit', () => Math.trunc(Number('3.2'))) //  62 ms
   

[Alessio Michelini]

Good to know, thanks!

[Teerasak Vichadee]

Kudos!