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Converting file size in bytes to human-readable string

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眼角桃花
眼角桃花 2020-11-28 17:58

I\'m using this function to convert a file size in bytes to a human-readable file size:

function getReadableFileSizeString(fileSizeInBytes) {
    var i = -1;
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19条回答
  • 情书的邮戳
    2020-11-28 18:25

    For those who use Angular, there's a package called angular-pipes that has a pipe for this:

    File

    import { BytesPipe } from 'angular-pipes';

    Usage

    {{ 150 | bytes }} <!-- 150 B -->
{{ 1024 | bytes }} <!-- 1 KB -->
{{ 1048576 | bytes }} <!-- 1 MB -->
{{ 1024 | bytes: 0 : 'KB' }} <!-- 1 MB -->
{{ 1073741824 | bytes }} <!-- 1 GB -->
{{ 1099511627776 | bytes }} <!-- 1 TB -->
{{ 1073741824 | bytes : 0 : 'B' : 'MB' }} <!-- 1024 MB -->

    Link to the docs.

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  • 孤独总比滥情好
    2020-11-28 18:26

    Another example similar to those here

    function fileSize(b) {
    var u = 0, s=1024;
    while (b >= s || -b >= s) {
        b /= s;
        u++;
    }
    return (u ? b.toFixed(1) + ' ' : b) + ' KMGTPEZY'[u] + 'B';
}

    It measures negligibly better performance than the others with similar features.

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  • 盖世英雄少女心
    2020-11-28 18:26 
    1551859712 / 1024 = 1515488
1515488 / 1024 = 1479.96875
1479.96875 / 1024 = 1.44528198242188

    Your solution is correct. The important thing to realize is that in order to get from 1551859712 to 1.5, you have to do divisions by 1000, but bytes are counted in binary-to-decimal chunks of 1024, hence why the Gigabyte value is less.

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  • 盖世英雄少女心
    2020-11-28 18:27

    Here is a prototype to convert a number to a readable string respecting the new international standards.

    There are two ways to represent big numbers: You could either display them in multiples of 1000 = 10 3 (base 10) or 1024 = 2 10 (base 2). If you divide by 1000, you probably use the SI prefix names, if you divide by 1024, you probably use the IEC prefix names. The problem starts with dividing by 1024. Many applications use the SI prefix names for it and some use the IEC prefix names. The current situation is a mess. If you see SI prefix names you do not know whether the number is divided by 1000 or 1024

    https://wiki.ubuntu.com/UnitsPolicy

    http://en.wikipedia.org/wiki/Template:Quantities_of_bytes

    Object.defineProperty(Number.prototype,'fileSize',{value:function(a,b,c,d){
 return (a=a?[1e3,'k','B']:[1024,'K','iB'],b=Math,c=b.log,
 d=c(this)/c(a[0])|0,this/b.pow(a[0],d)).toFixed(2)
 +' '+(d?(a[1]+'MGTPEZY')[--d]+a[2]:'Bytes');
},writable:false,enumerable:false});

    This function contains no loop, and so it's probably faster than some other functions.

    Usage:

    IEC prefix

    console.log((186457865).fileSize()); // default IEC (power 1024)
//177.82 MiB
//KiB,MiB,GiB,TiB,PiB,EiB,ZiB,YiB

    SI prefix

    console.log((186457865).fileSize(1)); //1,true for SI (power 1000)
//186.46 MB 
//kB,MB,GB,TB,PB,EB,ZB,YB

    i set the IEC as default because i always used binary mode to calculate the size of a file... using the power of 1024

    If you just want one of them in a short oneliner function:

    SI

    function fileSizeSI(a,b,c,d,e){
 return (b=Math,c=b.log,d=1e3,e=c(a)/c(d)|0,a/b.pow(d,e)).toFixed(2)
 +' '+(e?'kMGTPEZY'[--e]+'B':'Bytes')
}
//kB,MB,GB,TB,PB,EB,ZB,YB

    IEC

    function fileSizeIEC(a,b,c,d,e){
 return (b=Math,c=b.log,d=1024,e=c(a)/c(d)|0,a/b.pow(d,e)).toFixed(2)
 +' '+(e?'KMGTPEZY'[--e]+'iB':'Bytes')
}
//KiB,MiB,GiB,TiB,PiB,EiB,ZiB,YiB

    Usage:

    console.log(fileSizeIEC(7412834521));

    if you have some questions about the functions just ask

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  • 我寻月下人不归
    2020-11-28 18:30

    Based on cocco's idea, here's a less compact -but hopefully more comprehensive- example.

    <!DOCTYPE html>
<html>
<head>
<title>File info</title>

<script>
<!--
function fileSize(bytes) {
    var exp = Math.log(bytes) / Math.log(1024) | 0;
    var result = (bytes / Math.pow(1024, exp)).toFixed(2);

    return result + ' ' + (exp == 0 ? 'bytes': 'KMGTPEZY'[exp - 1] + 'B');
}

function info(input) {
    input.nextElementSibling.textContent = fileSize(input.files[0].size);
} 
-->
</script>
</head>

<body>
<label for="upload-file"> File: </label>
<input id="upload-file" type="file" onchange="info(this)">
<div></div>
</body>
</html>
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  • 盖世英雄少女心
    2020-11-28 18:30

    Based on cocco's answer but slightly desugerified (honestly, ones I was comfortable with are remained/added) and doesn't show trailing zeros but still supports 0, hope to be useful for others:

    function fileSizeSI(size) {
    var e = (Math.log(size) / Math.log(1e3)) | 0;
    return +(size / Math.pow(1e3, e)).toFixed(2) + ' ' + ('kMGTPEZY'[e - 1] || '') + 'B';
}


// test:
document.write([0, 23, 4322, 324232132, 22e9, 64.22e12, 76.22e15, 64.66e18, 77.11e21, 22e24].map(fileSizeSI).join('<br>'));

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