JSFiddle - React, Tailwind, and code Playground

HTML

<div id="bleh">

</div>

JavaScript

const l = 1024;
const R=10000000;
const a = new Float32Array(l);
const b = new Float32Array(l);
const c = new Float32Array(l);
  
const normal = function() {
	for(let i=0; i<l; i++) c[i] = a[i] + b[i];
}

const unroll = function() {
	for(let i=0; i<l; i+=8) {  
  	c[i  ] = a[i  ] + b[i  ];  c[i+1] = a[i+1] + b[i+1];  
    c[i+2] = a[i+2] + b[i+2];  c[i+3] = a[i+3] + b[i+3];  
    c[i+4] = a[i+4] + b[i+4];  c[i+5] = a[i+5] + b[i+5];  
    c[i+6] = a[i+6] + b[i+6];  c[i+7] = a[i+7] + b[i+7];  
  }
}

//reset
for(var i=0; i<l; i++) {  a[i]=i;  b[i]=3*i;  }
for(var r=0; r<R/100; r++) 
	normal();

//reset
for(var i=0; i<l; i++) {  a[i]=i;  b[i]=3*i;  }
for(var r=0; r<R/100; r++) 
	unroll();


//reset
for(var i=0; i<l; i++) {  a[i]=i;  b[i]=3*i;  }

//bench
let time = Date.now();
for(var r=0; r<R; r++) 
	normal();
var t0 = Date.now()-time;

//reset
for(var i=0; i<l; i++) {  a[i]=i;  b[i]=3*i;  }
//bench
time = Date.now();
for(var r=0; r<R; r++) 
	unroll();
let t1 = Date.now()-time;

document.getElementById("bleh").innerText = t0 + ", " + t1;
console.log(t0, t1);