我用的是这个函数。它适用于php和javascript。

    /**
     * @param $n
     * @return string
     * Use to convert large positive numbers in to short form like 1K+, 100K+, 199K+, 1M+, 10M+, 1B+ etc
     */
 function num_format($n) {
        $n_format = null;
        $suffix = null;
        if ($n > 0 && $n < 1000) {
           $n_format = Math.floor($n);   
            $suffix = '';
        }
        else if ($n == 1000) {
            $n_format = Math.floor($n / 1000);   //For PHP only use floor function insted of Math.floor()
            $suffix = 'K';
        }
        else if ($n > 1000 && $n < 1000000) {
            $n_format = Math.floor($n / 1000);
            $suffix = 'K+';
        } else if ($n == 1000000) {
            $n_format = Math.floor($n / 1000000);
            $suffix = 'M';
        } else if ($n > 1000000 && $n < 1000000000) {
            $n_format = Math.floor($n / 1000000);
            $suffix = 'M+';
        } else if ($n == 1000000000) {
            $n_format = Math.floor($n / 1000000000);
            $suffix = 'B';
        } else if ($n > 1000000000 && $n < 1000000000000) {
            $n_format = Math.floor($n / 1000000000);
            $suffix = 'B+';
        } else if ($n == 1000000000000) {
            $n_format = Math.floor($n / 1000000000000);
            $suffix = 'T';
        } else if ($n >= 1000000000000) {
            $n_format = Math.floor($n / 1000000000000);
            $suffix = 'T+';
        }


       /***** For PHP  ******/
       //  return !empty($n_format . $suffix) ? $n_format . $suffix : 0;

       /***** For Javascript ******/
        return ($n_format + $suffix).length > 0 ? $n_format + $suffix : 0;
    }

通过消除@martin-sznapka解决方案中的循环，您将减少40%的执行时间。

function formatNum(num,digits) {
    let units = ['k', 'M', 'G', 'T', 'P', 'E', 'Z', 'Y'];
    let floor = Math.floor(Math.abs(num).toString().length / 3);
    let value=+(num / Math.pow(1000, floor))
    return value.toFixed(value > 1?digits:2) + units[floor - 1];

}

速度测试(200000随机样本)从这个线程不同的解决方案

Execution time: formatNum          418  ms
Execution time: kFormatter         438  ms it just use "k" no "M".."T" 
Execution time: beautify           593  ms doesnt support - negatives
Execution time: shortenLargeNumber 682  ms    
Execution time: Intl.NumberFormat  13197ms 

/**
 * Shorten number to thousands, millions, billions, etc.
 * http://en.wikipedia.org/wiki/Metric_prefix
 *
 * @param {number} num Number to shorten.
 * @param {number} [digits=0] The number of digits to appear after the decimal point.
 * @returns {string|number}
 *
 * @example
 * // returns '12.5k'
 * shortenLargeNumber(12543, 1)
 *
 * @example
 * // returns '-13k'
 * shortenLargeNumber(-12567)
 *
 * @example
 * // returns '51M'
 * shortenLargeNumber(51000000)
 *
 * @example
 * // returns 651
 * shortenLargeNumber(651)
 *
 * @example
 * // returns 0.12345
 * shortenLargeNumber(0.12345)
 */
function shortenLargeNumber(num, digits) {
    var units = ['k', 'M', 'G', 'T', 'P', 'E', 'Z', 'Y'],
        decimal;

    for(var i=units.length-1; i>=0; i--) {
        decimal = Math.pow(1000, i+1);

        if(num <= -decimal || num >= decimal) {
            return +(num / decimal).toFixed(digits) + units[i];
        }
    }

    return num;
}

谢谢@Cos的评论，我删除了Math。round10依赖。

进一步改进Salman's Answer，因为它将nFormatter(33000)返回为33.0K

function nFormatter(num) {
     if (num >= 1000000000) {
        return (num / 1000000000).toFixed(1).replace(/\.0$/, '') + 'G';
     }
     if (num >= 1000000) {
        return (num / 1000000).toFixed(1).replace(/\.0$/, '') + 'M';
     }
     if (num >= 1000) {
        return (num / 1000).toFixed(1).replace(/\.0$/, '') + 'K';
     }
     return num;
}

now nFormatter(33000) = 33K

进一步改进Salman's Answer，因为像nFormatter(9999999,1)这样的情况返回1000K。

function formatNumberWithMetricPrefix(num, digits = 1) {
  const si = [
    {value: 1e18, symbol: 'E'},
    {value: 1e15, symbol: 'P'},
    {value: 1e12, symbol: 'T'},
    {value: 1e9, symbol: 'G'},
    {value: 1e6, symbol: 'M'},
    {value: 1e3, symbol: 'k'},
    {value: 0, symbol: ''},
  ];
  const rx = /\.0+$|(\.[0-9]*[1-9])0+$/;
  function divideNum(divider) {
    return (num / (divider || 1)).toFixed(digits);
  }

  let i = si.findIndex(({value}) => num >= value);
  if (+divideNum(si[i].value) >= 1e3 && si[i - 1]) {
    i -= 1;
  }
  const {value, symbol} = si[i];
  return divideNum(value).replace(rx, '$1') + symbol;
}

这里有一个简单的解决方案，可以避免所有的if语句(借助Math的力量)。

var SI_SYMBOL = ["", "k", "M", "G", "T", "P", "E"];

function abbreviateNumber(number){

    // what tier? (determines SI symbol)
    var tier = Math.log10(Math.abs(number)) / 3 | 0;

    // if zero, we don't need a suffix
    if(tier == 0) return number;

    // get suffix and determine scale
    var suffix = SI_SYMBOL[tier];
    var scale = Math.pow(10, tier * 3);

    // scale the number
    var scaled = number / scale;

    // format number and add suffix
    return scaled.toFixed(1) + suffix;
}

奖金模因

SI代表什么?