If you are looking for converting Large integers i.e. Numbers greater than Number.MAX_SAFE_INTEGER -- 9007199254740991, then you can use the following code

const hugeNumber = "9007199254740991873839" // Make sure its in String
const hexOfHugeNumber = BigInt(hugeNumber).toString(16);
console.log(hexOfHugeNumber)

You can do something like this in ECMAScript 6:

const toHex = num => (num).toString(16).toUpperCase();

As the accepted answer states, the easiest way to convert from decimal to hexadecimal is var hex = dec.toString(16). However, you may prefer to add a string conversion, as it ensures that string representations like "12".toString(16) work correctly.

// Avoids a hard-to-track-down bug by returning `c` instead of `12`
(+"12").toString(16);

To reverse the process you may also use the solution below, as it is even shorter.

var dec = +("0x" + hex);

It seems to be slower in Google Chrome and Firefox, but is significantly faster in Opera. See http://jsperf.com/hex-to-dec.

AFAIK comment 57807 is wrong and should be something like: var hex = Number(d).toString(16); instead of var hex = parseInt(d, 16);

function decimalToHex(d, padding) {
    var hex = Number(d).toString(16);
    padding = typeof (padding) === "undefined" || padding === null ? padding = 2 : padding;

    while (hex.length < padding) {
        hex = "0" + hex;
    }

    return hex;
}

function dec2hex(i)
{
  var result = "0000";
  if      (i >= 0    && i <= 15)    { result = "000" + i.toString(16); }
  else if (i >= 16   && i <= 255)   { result = "00"  + i.toString(16); }
  else if (i >= 256  && i <= 4095)  { result = "0"   + i.toString(16); }
  else if (i >= 4096 && i <= 65535) { result =         i.toString(16); }
  return result
}

Constrained/padded to a set number of characters:

function decimalToHex(decimal, chars) {
    return (decimal + Math.pow(16, chars)).toString(16).slice(-chars).toUpperCase();
}

var number = 3200;
var hexString = number.toString(16);

The 16 is the radix and there are 16 values in a hexadecimal number :-)

Combining some of these good ideas for an RGB-value-to-hexadecimal function (add the # elsewhere for HTML/CSS):

function rgb2hex(r,g,b) {
    if (g !== undefined)
        return Number(0x1000000 + r*0x10000 + g*0x100 + b).toString(16).substring(1);
    else
        return Number(0x1000000 + r[0]*0x10000 + r[1]*0x100 + r[2]).toString(16).substring(1);
}

function toHex(d) {
    return  ("0"+(Number(d).toString(16))).slice(-2).toUpperCase()
}

With padding:

function dec2hex(i) {
   return (i+0x10000).toString(16).substr(-4).toUpperCase();
}

为了完整起见，如果要用负数的二进制补码十六进制表示形式，则可以使用zero-fill-right shift >>>运算符。例如：

> (-1).toString(16)
"-1"

> ((-2)>>>0).toString(16)
"fffffffe"

但是，存在一个局限性：JavaScript按位运算符将其操作数视为32位序列，也就是说，您获得了32位二进制补码。

如果您需要处理位字段或32位颜色之类的内容，则需要处理带符号的数字。JavaScript函数toString(16)将返回负十六进制数，通常这不是您想要的。此功能做了一些疯狂的添加，使其成为正数。

function decimalToHexString(number)
{
  if (number < 0)
  {
    number = 0xFFFFFFFF + number + 1;
  }

  return number.toString(16).toUpperCase();
}

console.log(decimalToHexString(27));
console.log(decimalToHexString(48.6));

下面的代码会将十进制值d转换为十六进制。它还允许您将填充添加到十六进制结果中。因此，默认情况下0将变为00。

function decimalToHex(d, padding) {
    var hex = Number(d).toString(16);
    padding = typeof (padding) === "undefined" || padding === null ? padding = 2 : padding;

    while (hex.length < padding) {
        hex = "0" + hex;
    }

    return hex;
}

使用以下命令将数字转换为十六进制字符串：

hexString = yourNumber.toString(16);

并通过以下步骤逆转该过程：

yourNumber = parseInt(hexString, 16);