Question

请参阅代码段，javascript在计算数字时返回意外值。我正在使用最新的Firefox。有没有办法让我总能得到正确的价值？

console.log(100+59.59, "expected 159.59"); 
console.log(200+59.59, "expected 259.59");
console.log(300+59.59, "expected 359.59");
console.log(400+59.59, "expected 459.59");
console.log(500+59.59, "expected 559.59");
console.log(600+286.59, "expected 886.59");
console.log(700+286.59, "expected 986.59");

Answer 1

function FloatAdd(arg1, arg2)
{
  var r1, r2, m;
  try { r1 = arg1.toString().split(".")[1].length; } catch (e) { r1 = 0; }
  try { r2 = arg2.toString().split(".")[1].length; } catch (e) { r2 = 0; }
  m = Math.pow(10, Math.max(r1, r2));
  return (FloatMul(arg1, m) + FloatMul(arg2, m)) / m;
}

function FloatSubtraction(arg1, arg2)
{
  var r1, r2, m, n;
  try { r1 = arg1.toString().split(".")[1].length } catch (e) { r1 = 0 }
  try { r2 = arg2.toString().split(".")[1].length } catch (e) { r2 = 0 }
  m = Math.pow(10, Math.max(r1, r2));
  n = (r1 >= r2) ? r1 : r2;
  return ((arg1 * m - arg2 * m) / m).toFixed(n);
}

function FloatMul(arg1, arg2)
{
  var m = 0, s1 = arg1.toString(), s2 = arg2.toString();
  try { m += s1.split(".")[1].length; } catch (e) { }
  try { m += s2.split(".")[1].length; } catch (e) { }
  return Number(s1.replace(".", "")) * Number(s2.replace(".", "")) / Math.pow(10, m);
}

function FloatDiv(arg1, arg2)
{
  var t1 = 0, t2 = 0, r1, r2;
  try { t1 = arg1.toString().split(".")[1].length } catch (e) { }
  try { t2 = arg2.toString().split(".")[1].length } catch (e) { }
  with (Math)
  {
    r1 = Number(arg1.toString().replace(".", ""))
    r2 = Number(arg2.toString().replace(".", ""))
    return (r1 / r2) * pow(10, t2 - t1);
  }
}

参考http://kevintsengtw.blogspot.tw/2011/09/javascript.html

这个问题在这里已有答案：
   Is floating point math broken?

所以快速的方法是转换为字符串，然后再次更改为浮动以修复它

Answer 2

如果您确定不需要超过x小数位，则可以使用toFixed()方法，如下所示：

＆＃13;

console.log((100+59.59).toFixed(2), "expected 159.59"); 
console.log((200+59.59).toFixed(2), "expected 259.59");
console.log((300+59.59).toFixed(2), "expected 359.59");
console.log((400+59.59).toFixed(2), "expected 459.59");
console.log((500+59.59).toFixed(2), "expected 559.59");
console.log((600+286.59).toFixed(2), "expected 886.59");
console.log((700+286.59).toFixed(2), "expected 986.59");

＆＃13;

这里的问题不是Javascript，而是二进制中浮点数的限制。 0.59不能用64位浮点数完美表示（当转换回十进制时，它实际上用于0.58999999999999996891375531049561686813831329345703125。）

Javascript在计算数字时返回意外值

2 个答案: