希望能在运算效率上再加强

[Midas-Li]

我做了一下压力测试，感觉效率上有改进的余地：

describe('求余数运算', () => {

//Math.round 用时14ms
it('test Math', () => {
let total=0;
for (let i = 1; i <= 10000 * 10; i++) {
total += Math.round(i * 100) / 100;
}
console.log(total);
});

//Math.round 再加上求精度，转浮点数，用时 273ms
it('test Math2', () => {
let total=0;
for (let i = 1; i <= 10000 * 10; i++) {
total += Math.round(parseFloat((i * 100).toPrecision(14))) / 100;
}
console.log(total);
});

//NP.round 用时1sec963ms
it('test NP', () => {
let total=0;
for (let i = 1; i <= 10000 * 10; i++) {
total += NP.round(i ,2) ;
}
console.log(total);
});
})

[Midas-Li]

我利用空余时间也写了一个：
function extendNumDoubles(n: number, timesNum: number): number {
let s = n.toString();
let index = s.indexOf('.');
if (index === -1)
return Number(s + '0'.repeat(timesNum));
else {
let strLen = s.length;
let numPointPos = index + 1 + timesNum;

  let s2 =
        s.slice(0, index) +   //小数点前的数字
        s.slice(index + 1, numPointPos) +//原小数点后和新小数点前的数字
        (numPointPos <= strLen ? '.' : '') + //新小数点
        s.slice(numPointPos) +   //新小数点后的数字
        (numPointPos - strLen > 0 ? '0'.repeat(numPointPos - strLen) : '');  //补零
  
  return parseFloat(s2);
  
}

}

function toDecimalRound(x: number, digit: number): number {
digit = Math.abs(digit);
return Math.round(extendNumDoubles(Number(x.toPrecision(13)), digit)) / Math.pow(10, digit);
}

用了268ms的时间：
it('test Math toDecimalRound 268ms', () => {
let total = 0;
for (let i = 1; i <= 10000 * 10; i++) {
total += toDecimalRound(i,2);
}
console.log(total);
});