基于@ michazperzhaakowski的回答(EcmaScipt 6)和他基于Tim Down的回答的回答

我写了一个转换hexToRGB函数的修改版本，增加了安全检查r/g/b颜色组件是否在0-255之间，而且函数可以接受数字r/g/b参数或字符串r/g/b参数，如下所示:

 function rgbToHex(r, g, b) {
     r = Math.abs(r);
     g = Math.abs(g);
     b = Math.abs(b);

     if ( r < 0 ) r = 0;
     if ( g < 0 ) g = 0;
     if ( b < 0 ) b = 0;

     if ( r > 255 ) r = 255;
     if ( g > 255 ) g = 255;
     if ( b > 255 ) b = 255;

    return '#' + [r, g, b].map(x => {
      const hex = x.toString(16);
      return hex.length === 1 ? '0' + hex : hex
    }).join('');
  }

为了安全地使用这个函数——你应该检查传递的字符串是否是真正的rbg字符串颜色——例如，一个非常简单的检查可以是:

if( rgbStr.substring(0,3) === 'rgb' ) {

  let rgbColors = JSON.parse(rgbStr.replace('rgb(', '[').replace(')', ']'))
  rgbStr = this.rgbToHex(rgbColors[0], rgbColors[1], rgbColors[2]);

  .....
}

看起来你在寻找这样的东西:

function hexstr(number) {
    var chars = new Array("0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "a", "b", "c", "d", "e", "f");
    var low = number & 0xf;
    var high = (number >> 4) & 0xf;
    return "" + chars[high] + chars[low];
}

function rgb2hex(r, g, b) {
    return "#" + hexstr(r) + hexstr(g) + hexstr(b);
}

hexToRgb的另一个版本:

function hexToRgb(hex) {
    var bigint = parseInt(hex, 16);
    var r = (bigint >> 16) & 255;
    var g = (bigint >> 8) & 255;
    var b = bigint & 255;

    return r + "," + g + "," + b;
}

编辑:3/28/2017 这是另一种似乎更快的方法

function hexToRgbNew(hex) {
  var arrBuff = new ArrayBuffer(4);
  var vw = new DataView(arrBuff);
  vw.setUint32(0,parseInt(hex, 16),false);
  var arrByte = new Uint8Array(arrBuff);

  return arrByte[1] + "," + arrByte[2] + "," + arrByte[3];
}

编辑:8/11/2017 经过更多测试后，上面的新方法并没有更快:(。虽然这是一种有趣的替代方式。

function getRGB(color){
  if(color.length == 7){
    var r = parseInt(color.substr(1,2),16);
    var g = parseInt(color.substr(3,2),16);
    var b = parseInt(color.substr(5,2),16);    
    return 'rgb('+r+','+g+','+b+')' ;
  }    
  else
    console.log('Enter correct value');
}
var a = getRGB('#f0f0f0');
if(!a){
 a = 'Enter correct value'; 
}

a;

上面的一个干净的咖啡脚本版本(谢谢@TimDown):

rgbToHex = (rgb) ->
    a = rgb.match /\d+/g
    rgb  unless a.length is 3
    "##{ ((1 << 24) + (parseInt(a[0]) << 16) + (parseInt(a[1]) << 8) + parseInt(a[2])).toString(16).slice(1) }"

从HEX转换为RGB，其中RGB是0到1范围内的浮点值:

#FFAA22→{r: 0.5, g: 0, b:1}

我改编了@Tim Down的回答:

function convertRange(value,oldMin,oldMax,newMin,newMax) {
  return (Math.round(((((value - oldMin) * (newMax - newMin)) / (oldMax - oldMin)) + newMin) * 10000)/10000)
}

function hexToRgbFloat(hex) {
  var result = /^#?([a-f\d]{2})([a-f\d]{2})([a-f\d]{2})$/i.exec(hex);
  return result ? {
    r: convertRange(parseInt(result[1],16), 0, 255, 0, 1),
    g: convertRange(parseInt(result[2],16), 0, 255, 0, 1),
    b: convertRange(parseInt(result[3],16), 0, 255, 0, 1)
  } : null;
}

console.log(hexToRgbFloat("#FFAA22")) // {r: 1, g: 0.6667, b: 0.1333}