JS 四舍五入

function format_number(srcNumber, n) {
var dstNumber = parseFloat(srcNumber);
if (isNaN(dstNumber)) {
return srcNumber;
}
if (dstNumber >= 0) {
dstNumber = parseInt(dstNumber * Math.pow(10, n) + 0.5) / Math.pow(10, n);
} else {
var tmpDstNumber = -dstNumber; dstNumber = parseInt(tmpDstNumber * Math.pow(10, n) + 0.5) / Math.pow(10, n);
}
var dstStrNumber = dstNumber.toString();
var dotIndex = dstStrNumber.indexOf(‘.‘);
if (dotIndex < 0) {
dotIndex = dstStrNumber.length; dstStrNumber += ‘.‘;
}

while (dstStrNumber.length <= dotIndex + n) {
dstStrNumber += ‘0‘;
}
return dstStrNumber;
}