JS 格式化字节单位为 kb, m, g 等为友好大小单位

经常用到的JS单位转换函数:

function format_size(bytes) {
       if (bytes === 0) return ‘0 B’;
        var k = 1024;
        sizes = [‘B’,’KB’, ‘MB’, ‘GB’, ‘TB’, ‘PB’, ‘EB’, ‘ZB’, ‘YB’];
        i = Math.floor(Math.log(bytes) / Math.log(k));
    return (bytes / Math.pow(k, i)).toPrecision(2) + ‘ ‘ + sizes[i];
       //toPrecision(3) 后面保留一位小数，如1.0GB                                                       //return (bytes / Math.pow(k, i)).toPrecision(3) + ‘ ‘ + sizes[i];
       //bytes / Math.pow(1024, Math.floor(Math.log(bytes) / Math.log(1024)))
    }