a1 = raw_input("please input a number")
a = int(a1)
if(a!=0):
if(a > 0):
print '这是正数'
if(a < 0 ):
print '这是负数'
else:
print 'the number is equal to 0'

Number.isInteger(25); //true
Number.isInteger(25.222); //false
Number.isInteger('25'); // false
Number.isInteger('25.222'); //false
Number.isInteger('foo'); // false

function numberIsInteger(n){
  if(!Number.isInteger){
    return typeof n === 'number' && Math.round(n) === n;
  }
  return n;
}

function numberIsInteger(n){
  if(!Number.isInteger){
    return typeof n === 'number' && n % 1 === 0;
  }
  return Number.isInteger(n);
}

console.log(Math.sign(-5)); //-1
console.log(Math.sign(-5.222)); // -1
console.log(Math.sign(555)); // 1
console.log(Math.sign(0)); // 0
console.log(Math.sign(-0)); // -0
console.log(Math.sign('foo')); // NaN

Math.sign = Math.sign || function (n){
  n = +n;
  if(n === 0 || isNaN(n)){
    return n;
  }
  return x > 0 ? 1 : -1;
}