格式化数字
function formatNumber(num, digits) {
const si = [
{value:1E18, symbol:'E' },
{value:1E15, symbol:'P' },
{value:1E12, symbol:'T' },
{value:1E9, symbol:'G' },
{value:1E6, symbol:'M' },
{value:1E3, symbol:'k' }
]
for (let i =0; i < si.length; i++) {
if (num >= si[i].value) {
return (num / si[i].value +0.1).toFixed(digits).replace(/\.0+$|(\.[0-9]*[1-9])0+$/, '$1') + si[i].symbol
}
}
return num.toString()
}