Angular2 + TypeScript file size Pipe/Filter. Convert bytes into largest possible unit. e.g. 1024 => 1 KB

file-size.pipe.ts

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import { Pipe, PipeTransform } from '@angular/core';

type unit = 'bytes' | 'KB' | 'MB' | 'GB' | 'TB' | 'PB';
type unitPrecisionMap = {
  [u in unit]: number;
};

const defaultPrecisionMap: unitPrecisionMap = {
  bytes: 0,
  KB: 0,
  MB: 1,
  GB: 1,
  TB: 2,
  PB: 2
};

/*
 * Convert bytes into largest possible unit.
 * Takes an precision argument that can be a number or a map for each unit.
 * Usage:
 *   bytes | fileSize:precision
 * @example
 * // returns 1 KB
 * {{ 1500 | fileSize }}
 * @example
 * // returns 2.1 GB
 * {{ 2100000000 | fileSize }}
 * @example
 * // returns 1.46 KB
 * {{ 1500 | fileSize:2 }}
 */
@Pipe({ name: 'fileSize' })
export class FileSizePipe implements PipeTransform {
  private readonly units: unit[] = ['bytes', 'KB', 'MB', 'GB', 'TB', 'PB'];

  transform(bytes: number = 0, precision: number | unitPrecisionMap = defaultPrecisionMap): string {
    if (isNaN(parseFloat(String(bytes))) || !isFinite(bytes)) return '?';

    let unitIndex = 0;

    while (bytes >= 1024) {
      bytes /= 1024;
      unitIndex++;
    }

    const unit = this.units[unitIndex];

    if (typeof precision === 'number') {
      return `${bytes.toFixed(+precision)} ${unit}`;
    }
    return `${bytes.toFixed(precision[unit])} ${unit}`;
  }
}

A simple suggestion. if (unit == 0) precision = 0; after the while loop so you don't end up with "38.00 bytes."

I guess this wouldn't help if you were averaging file sizes or something but I bet total file size is it's more popular use.

And what about this one...

let unit = 0, division = bytes;
    
    while ( division >= 1024 ) {
      division /= 1024;
      unit ++;
    }
    if (bytes % 1024 <= 10) precision = 0;

I found it cleaner to change:
while ( bytes >= 1024 ) {
to:
while ( bytes >= 1000 ) {
to avoid having something like 1021 kB. This would be rounded down to 1 MB which looks better.

Added a file size precision map so you can have more finite control over what precision you want per unit.
It still accepts a number for the same precision across all units.

There is a small issue if the bytes is int value, will raise error bytes.toFixed is not a function, a quick fix is convert to float before run toFixed, bytes = parseFloat(bytes.toString());

 import { Pipe, PipeTransform } from '@angular/core';

 const FILE_SIZE_UNITS = ['B', 'KB', 'MB', 'GB', 'TB', 'PB', 'EB', 'ZB', 'YB'];
 const FILE_SIZE_UNITS_LONG = ['Bytes', 'Kilobytes', 'Megabytes', 'Gigabytes', 'Pettabytes', 'Exabytes', 'Zettabytes', 'Yottabytes'];

 @Pipe({
   name: 'formatFileSize'
 })
 export class FormatFileSizePipe implements PipeTransform {
    transform(sizeInBytes: number, longForm: boolean): string {
     const units = longForm
       ? FILE_SIZE_UNITS_LONG
       : FILE_SIZE_UNITS;

     let power = Math.round(Math.log(sizeInBytes) / Math.log(1024));
     power = Math.min(power, units.length - 1);

const size = sizeInBytes / Math.pow(1024, power); // size in new units
const formattedSize = Math.round(size * 100) / 100; // keep up to 2 decimals
const unit = units[power];

return `${formattedSize} ${unit}`;
   }
 }
   }

nice, thanks