单位转换：将kb转换为 MB ，GB等形式

写法一：

function formatSizeUnits(kb) {
    let units = ['KB', 'MB', 'GB', 'TB', 'PB','EB','ZB','YB'];
    let unitIndex = 0;

    while (kb >= 1024 && unitIndex < units.length - 1) {
        kb /= 1024;
        unitIndex++;
    }

    return `${kb.toFixed(2)} ${units[unitIndex]}`;
}
console.log(formatSizeUnits(1034000320))

写法二： 

function formatSizeUnits(kb) {
    let units = ['KB', 'MB', 'GB', 'TB', 'PB','EB','ZB','YB'];
    let unitIndex = 0;
    let unit = ''

    for(let i=1;i<units.length+1;i++){
        if(kb>=1024&i<units.length){
            kb=kb/1024;
            unit = units[i]
            // console.log('if',kb,i,unit)
        } else {
            unit = units[i-1]
            // console.log('else',kb,i,unit)
            return `${kb.toFixed(2)} ${unit}`;
        }
    }
    
}
console.log(formatSizeUnits(1034000320))