How to convert Hex to RGBA value using JavaScript ? - GeeksforGeeks

31 Dec, 2019
Given a color hex code and the task is to convert Hex Value to RGBA value. Here are few of the mostly techniques discussed with the help of JavaScript.
Approach 1:
First check the passed Hex value is valid or not through a Regular Expression.
Then get the hex value content after ‘#’ by using .slice() method and use .split() method to get the every character of the hex value in the array.
If the length of array is 3(eg. #fff, #aaa) then store them as(eg. #ffffff, #aaaaaa respectively) to make the length 6.
Transform the code to Hexadecimal as first 2 character belongs to Red Value, mid 2 character belongs to Green value and so on.
Example: This example uses the approach discussed above.
<!DOCTYPE HTML> <html>   <head>     <title>         How to convert Hex value to RGBA        value using JavaScript    </title></head>   <body style = "text-align:center;">           <h1 style = "color: green">         GeeksForGeeks     </h1>          <p id = "GFG_UP" style =        "font-size: 20px; font-weight: bold;">    </p>          <button onclick = "gfg_Run()">         Click Here    </button>          <p id = "GFG_DOWN" style = "color:green;        font-size: 26px; font-weight: bold;">    </p>          <script>        var el_up = document.getElementById("GFG_UP");        var el_down = document.getElementById("GFG_DOWN");        var hexValue = '#fbafff';                  el_up.innerHTML = "Click on the button to"                + " get the RGBA value of Hex "                + "Value.<br>HexValue = '" +                 hexValue + "'";                  function convertHexToRgbA(hexVal) {            var ret;                          // If the hex value is valid.            if(/^#([A-Fa-f0-9]{3}){1,2}$/.test(hexVal)) {                                  // Getting the content after '#',                // eg. 'ffffff' in case of '#ffffff'                ret = hexVal.slice(1);                                  // Splitting each character                ret = ret.split('');                                  // Checking if the length is 3                // then make that 6                if(ret.length == 3) {                    var ar = [];                    ar.push(ret[0]);                     ar.push(ret[0]);                    ar.push(ret[1]);                    ar.push(ret[1]);                    ar.push(ret[2]);                    ar.push(ret[2]);                    ret = ar;                }                                  // Starts with '0x'(in hexadecimal)                ret = '0x'+ ret.join('');                                  // Converting the first 2 characters                // from hexadecimal to r value                var r = (ret>>16)&255;                                  // Converting the second 2 characters                // to hexadecimal to g value                var g = (ret>>8)&255;                                  // Converting the last 2 characters                // to hexadecimal to b value                var b = ret&255;                                  // Appending all of them to make                // the RGBA value                return 'rgba('+[r, g, b].join(',')+',1)';            }        }        function gfg_Run() {            el_down.innerHTML = "The RGBA value of '"                + hexValue + "' is '" +                 convertHexToRgbA(hexValue) + "'";        }     </script> </body>   </html>
Output:
Before clicking on the button:
After clicking on the button:
Approach 2:
Use .slice() method to get the first 2 characters and convert them to Hexadecimal.
Repeat the step 1 for every 2 characters for rest of the code.
Append them together and return the final value.
Example: This example uses the approach discussed above.
<!DOCTYPE HTML> <html>   <head>     <title>         How to convert Hex value to RGBA        value using JavaScript ?    </title>          <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.4.1/jquery.min.js">    </script></head>   <body style = "text-align:center;">           <h1 style = "color: green">         GeeksForGeeks     </h1>          <p id = "GFG_UP" style =         "font-size: 20px; font-weight: bold;">    </p>          <button onclick = "gfg_Run()">         Click Here    </button>          <p id = "GFG_DOWN" style = "color:green;        font-size: 26px; font-weight: bold;">    </p>          <script>        var el_up = document.getElementById("GFG_UP");        var el_down = document.getElementById("GFG_DOWN");        var hexValue = '#fbafff';                  el_up.innerHTML = "Click on the button to get"                + " the RGBA value of Hex Value."                + "<br>HexValue = '" + hexValue + "'";                  function convertHexToRgbA(hex, a) {                          // Convert the first 2 characters to hexadecimal            var r = parseInt(hex.substring(1, 3), 16),                          // Convert the middle 2 characters to hexadecimal            g = parseInt(hex.substring(3, 5), 16),                              // Convert the last 2 characters to hexadecimal            b = parseInt(hex.substring(5, 7), 16);                              // append them all            return "rgba(" + r + ", " + g + ", "                    + b + ", " + a + ")";        }                  function gfg_Run() {            el_down.innerHTML = "The RGBA value of '"                    + hexValue + "' is '" +                     convertHexToRgbA(hexValue, 1) + "'";        }     </script> </body>   </html>
Output:
Before clicking on the button:
After clicking on the button:
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