也许你还需要小数分隔符?这是我刚刚创建的一个函数:

function formatFloat(num,casasDec,sepDecimal,sepMilhar) {
    if (num < 0)
    {
        num = -num;
        sinal = -1;
    } else
        sinal = 1;
    var resposta = "";
    var part = "";
    if (num != Math.floor(num)) // decimal values present
    {
        part = Math.round((num-Math.floor(num))*Math.pow(10,casasDec)).toString(); // transforms decimal part into integer (rounded)
        while (part.length < casasDec)
            part = '0'+part;
        if (casasDec > 0)
        {
            resposta = sepDecimal+part;
            num = Math.floor(num);
        } else
            num = Math.round(num);
    } // end of decimal part
    while (num > 0) // integer part
    {
        part = (num - Math.floor(num/1000)*1000).toString(); // part = three less significant digits
        num = Math.floor(num/1000);
        if (num > 0)
            while (part.length < 3) // 123.023.123  if sepMilhar = '.'
                part = '0'+part; // 023
        resposta = part+resposta;
        if (num > 0)
            resposta = sepMilhar+resposta;
    }
    if (sinal < 0)
        resposta = '-'+resposta;
    return resposta;
}

有一些函数可以取整数字。例如:

var x = 5.0364342423;
print(x.toFixed(2));

将打印5.04。

编辑: 小提琴

var result = Math.round(original*100)/100;

具体细节，以防代码不是自解释的。

编辑:…或者直接使用toFixed，就像Tim Büthe提议的那样。忘记了，谢谢你的提醒(还有点赞):)

function trimNumber(num, len) {
  const modulu_one = 1;
  const start_numbers_float=2;
  var int_part = Math.trunc(num);
  var float_part = String(num % modulu_one);
      float_part = float_part.slice(start_numbers_float, start_numbers_float+len);
  return int_part+'.'+float_part;
}

var x = 0.3445434
x = Math.round (x*100) / 100 // this will make nice rounding

我使用这段代码来格式化浮动。它基于toPrecision()，但它去掉了不必要的零。我欢迎关于如何简化正则表达式的建议。

function round(x, n) {
    var exp = Math.pow(10, n);
    return Math.floor(x*exp + 0.5)/exp;
}

使用的例子:

function test(x, n, d) {
    var rounded = rnd(x, d);
    var result = rounded.toPrecision(n);
    result = result.replace(/\.?0*$/, '');
    result = result.replace(/\.?0*e/, 'e');
    result = result.replace('e+', 'e');
    return result;  
}

document.write(test(1.2000e45, 3, 2) + '=' + '1.2e45' + '<br>');
document.write(test(1.2000e+45, 3, 2) + '=' + '1.2e45' + '<br>');
document.write(test(1.2340e45, 3, 2) + '=' + '1.23e45' + '<br>');
document.write(test(1.2350e45, 3, 2) + '=' + '1.24e45' + '<br>');
document.write(test(1.0000, 3, 2) + '=' + '1' + '<br>');
document.write(test(1.0100, 3, 2) + '=' + '1.01' + '<br>');
document.write(test(1.2340, 4, 2) + '=' + '1.23' + '<br>');
document.write(test(1.2350, 4, 2) + '=' + '1.24' + '<br>');