Edit in JSFiddle

var k, A = [];
for (k=2; k<=100; k++) {
	A[k] = 1;	
}
for (m=2; m<=10; m++) {
	document.write('<br>' + m +'の倍数:');
	for (k=2*m; k<=100; k+=m) {
    	document.write(k + ',');
		A[k] = 0;
	}
}
document.write('<br><br>素数は...<br>');
for (k=2; k<=100; k++) {
	if (A[k] != 0) {
		document.write(k + ',');
	}
}