toFixed方法改写

Number.prototype.toFixed = function (s) {    const adjust = this > 0 ? 0.5 : -0.5;    let numThe = (parseInt(this * Math.pow(10, s) + 0.5 )/ Math.pow(10, s)).toString();    let index = numThe.indexOf('.');    if (index < 0 && s > 0) {        numThe = numThe + '.';        for(let i = 0; i< s; i++){            numThe = numThe + '0';        }    } else {        index = numThe - index;        for (let i = 0; i < (s - index) + 1; i++) {            numThe = numThe + '0'        }    }    return numThe;}