JavaScript中的小数

Question

如何在javascript中转换此输出：

a = 1.0000006

b = 0.00005

c = 2.54695621e-7

到此输出：

a = 1

b = 5e-5

c = 2.547e-7

Answer 1

尝试以下代码：

 var a = 1.0000006; var b = 0.00005; var c = 2.54695621e-7; var a_Result = Math.round(a); var b_Result = b.toExponential(); var c_Result = c.toExponential(3); console.log(a_Result ); console.log(b_Result); console.log(c_Result); 

Answer 2

使用此输入：

var nums = [1.0000006, 0.00005, 2.54695621e-7];

您可以使用Number#toExponential获取具有一定精度的指数表示法：

function formatNumber(n) {
    return n.toExponential(3);
}

nums.map(formatNumber)
// ["1.000e+0", "5.000e-5", "2.547e-7"]

分成有用的部分：

function formatNumber(n) {
    return n
        .toExponential(3)
        .split(/[.e]/);
}

nums.map(formatNumber)
// [["1", "000", "+0"], ["5", "000", "-5"], ["2", "547", "-7"]]

并删除不必要的内容：

function formatNumber(n) {
    var parts = n
        .toExponential(3)
        .split(/[.e]/);

    var integral = parts[0];
    var fractional = '.' + parts[1];
    var exponent = 'e' + parts[2];

    fractional = fractional.replace(/\.?0+$/, '');
    exponent = exponent === 'e+0' ? '' : exponent;

    return integral + fractional + exponent;
}

nums.map(formatNumber)
// ["1", "5e-5", "2.547e-7"]

ES6：

const formatNumber = n => {
    const [, integral, fractional, exponent] =
        /(\d+)(\.\d+)(e.\d+)/.exec(n.toExponential(3));

    return integral +
        fractional.replace(/\.?0+$/, '') +
        (exponent === 'e+0' ? '' : exponent);
};