jQuery set CSS background opacity

Question

I have a

whose transparency of its background-color (and not its contents) I\'d like to change. A remote API sends me this colour:

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Answer 1

You may try this

function convertHex(hex,opacity){
    hex = hex.replace('#','');
    r = parseInt(hex.substring(0,2), 16);
    g = parseInt(hex.substring(2,4), 16);
    b = parseInt(hex.substring(4,6), 16);
    result = 'rgba('+r+','+g+','+b+','+opacity/100+')';
    return result;
}

$('h1').css('background', convertHex('#A7D136', 0.5));

An example here.

Answer 2

try parseInt(hex,16) to convert hex string into decimal int

so in this case it'll be:

var color = '#abcdef';
var rgbaCol = 'rgba(' + parseInt(color.slice(-6,-4),16)
    + ',' + parseInt(color.slice(-4,-2),16)
    + ',' + parseInt(color.slice(-2),16)
    +',0.5)';
$('div').css('background-color', rgbaCol)

you should create a function out of this to use in your application.

Answer 3

You may use this javascript helper function

function setColorOpacity(colorStr, opacity) {
  if(colorStr.indexOf("rgb(") == 0)
  {
    var rgbaCol = colorStr.replace("rgb(", "rgba(");
    rgbaCol = rgbaCol.replace(")", ", "+opacity+")");
    return rgbaCol;
  }

  if(colorStr.indexOf("rgba(") == 0)
  {
    var rgbaCol = colorStr.substr(0, colorStr.lastIndexOf(",")+1) + opacity + ")";
    return rgbaCol;
  }

  if(colorStr.length == 6)
    colorStr = "#" + colorStr;

  if(colorStr.indexOf("#") == 0)
  {
    var rgbaCol = 'rgba(' + parseInt(colorStr.slice(-6, -4), 16)
        + ',' + parseInt(colorStr.slice(-4, -2), 16)
        + ',' + parseInt(colorStr.slice(-2), 16)
        + ','+opacity+')';
    return rgbaCol;
  }
  return colorStr;
}

Answer 4

This should work for you. It does assume that you are passing a valid 6 digit hex code and an opacity, and does no error checking.

function hex2rgba(hex, opacity)
{
    //extract the two hexadecimal digits for each color
    var patt = /^#([\da-fA-F]{2})([\da-fA-F]{2})([\da-fA-F]{2})$/;
    var matches = patt.exec(hex);

    //convert them to decimal
    var r = parseInt(matches[1], 16);
    var g = parseInt(matches[2], 16);
    var b = parseInt(matches[3], 16);

    //create rgba string
    var rgba = "rgba(" + r + "," + g + "," + b + "," + opacity + ")";

    //return rgba colour
    return rgba;
}

$(".box").css("background-color", hex2rgba("#ABCDEF", 0.6));

You can view an example of this on jsFiddle here