Will Math.random show speed?

Can I use Javascript to throw the computer a bunch of random mathematical equations, then have it tell me the time taken for the operation?

Will this give a true and accurate representation about the speed of a computer?

I created a sample Javascript code just to document.write numbers up till 50,000.

var start = new Date().getTime();

document.write("<h1>Start</h1><br><h3>Time taken:</h3>");

for (i = 0; i <= 50000; ++i) {               
document.write(i+"\n");
}

var end = new Date().getTime();
var time = end - start;

document.write("<h1>Success.</h1>");



alert("For the program to execute, it took this computer... \n\n" + time + " milliseconds.\n\nOperation was SUCCESSFUL. ✓");