function bytesToSize(bytes) { var sizes = ['B', 'K', 'M', 'G', 'T', 'P']; for (var i = 0; i < sizes.length; i++) { if (bytes <= 1024) { return bytes + ' ' + sizes[i]; } else { bytes = parseFloat(bytes / 1024).toFixed(2) } } return bytes + ' P'; } console.log(bytesToSize(234)); console.log(bytesToSize(2043)); console.log(bytesToSize(20433242)); console.log(bytesToSize(2043324243)); console.log(bytesToSize(2043324268233)); console.log(bytesToSize(2043324268233343));

这是一个字节应该如何显示给人类:

function bytesToHuman(bytes, decimals = 2) {
  // https://en.wikipedia.org/wiki/Orders_of_magnitude_(data)
  const units = ["bytes", "KiB", "MiB", "GiB", "TiB", "PiB", "EiB"]; // etc

  let i = 0;
  let h = 0;

  let c = 1 / 1023; // change it to 1024 and see the diff

  for (; h < c && i < units.length; i++) {
    if ((h = Math.pow(1024, i) / bytes) >= c) {
      break;
    }
  }

  // remove toFixed and let `locale` controls formatting
  return (1 / h).toFixed(decimals).toLocaleString() + " " + units[i];
}

// test
for (let i = 0; i < 9; i++) {
  let val = i * Math.pow(10, i);
  console.log(val.toLocaleString() + " bytes is the same as " + bytesToHuman(val));

}

// let's fool around
console.log(bytesToHuman(1023));
console.log(bytesToHuman(1024));
console.log(bytesToHuman(1025));

试试这个简单的解决方法。

var files = $("#file").get(0).files;               
                var size = files[0].size;
                if (size >= 5000000) {
alert("File size is greater than or equal to 5 MB");
}

这里有一句话:

val => ['Bytes','Kb','Mb','Gb','Tb'][Math.floor(Math.log2(val)/10)]

甚至:

v => 'BKMGT'[~~(Math.log2(v)/10)]

与数:

function shortenBytes(n) {
    const k = n > 0 ? Math.floor((Math.log2(n)/10)) : 0;
    const rank = (k > 0 ? 'KMGT'[k - 1] : '') + 'b';
    const count = Math.floor(n / Math.pow(1024, k));
    return count + rank;
}

我最初在一个文件上传项目中使用@ al冰岛jm的答案，但最近遇到了一个问题，一个文件是0.98kb，但读取为1.02mb。下面是我现在使用的更新代码。

function formatBytes(bytes){
  var kb = 1024;
  var ndx = Math.floor( Math.log(bytes) / Math.log(kb) );
  var fileSizeTypes = ["bytes", "kb", "mb", "gb", "tb", "pb", "eb", "zb", "yb"];

  return {
    size: +(bytes / kb / kb).toFixed(2),
    type: fileSizeTypes[ndx]
  };
}

在像这样添加文件之后，上面的函数将被调用

// In this case `file.size` equals `26060275` 
formatBytes(file.size);
// returns `{ size: 24.85, type: "mb" }`

当然，Windows读取的文件为24.8mb，但我对额外的精度很满意。

我正在更新@ al冰岛的答案。由于小数点对于1,2位数的数字很重要，所以我舍入了第一个小数点并保留第一个小数点。对于3位数的数字，我舍入个位数，忽略所有小数点后的位置。

getMultiplers : function(bytes){
    var unit = 1000 ;
    if (bytes < unit) return bytes ;
    var exp = Math.floor(Math.log(bytes) / Math.log(unit));
    var pre = "kMGTPE".charAt(exp-1);
    var result = bytes / Math.pow(unit, exp);
    if(result/100 < 1)
        return (Math.round( result * 10 ) / 10) +pre;
    else
        return Math.round(result) + pre;
}