1，
lcm=function(m,n){//辗转相除法 求最大公约数 var u=+m,v=+n,t=v; while(v!=0){ t=u%v; u=v; v=t; } return u }
2，
function commonDivisor2(num1,num2) {//更相减损法
var index=0;
while (num1%2==0 && num2%2 ==0) {
num1 = num1/2;
num2 = num2/2;
index += 1;
}
if ((num1-num2) < 0) {
var k = num1;
num1 = num2;
num2 = k;
}
var cha = num1-num2;
while (cha != num2) {
if (cha -num2>0) {
num1 = cha;
} else {
num1 = num2;
num2 = cha;
}
cha = num1-num2;
}
if (index == 0) {
return cha;
} else {
return cha*index*2;
}
}