JSFiddle - React, Tailwind, and code Playground

JavaScript

var l = 1024, R=1000000;
var a = new Uint32Array(l);
var b = new Uint32Array(l);
var c = new Uint32Array(l);

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

var time = Date.now();

for(var r=0; r<R; r++) 
	for(var i=0; i<l; i++) c[i] = a[i] + b[i];
  
var t0 = Date.now()-time;  time = Date.now();

for(var r=0; r<R; r++) 
	for(var 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];  
  }

var t1 = Date.now()-time;

alert(t0 + ", "+ t1);