How to convert Hex value to RGBA value using JavaScript?-JS Tutorial-php.cn

How to convert Hex value to RGBA value using JavaScript?

王林

Release： 2023-08-31 14:01:02

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如何使用 JavaScript 将 Hex 值转换为 RGBA 值？

When designing web pages, we use colors to make the web pages more attractive and attractive. We usually use hexadecimal codes to represent colors, but sometimes we need to add transparency to a color, which can be achieved through RGBA values.

Hexadecimal color values are represented by #RRGGBBAA, RGBA color values are represented by rgba(red, green, blue, alpha). Here are some examples of RGBA and hexadecimal values -

Input:     #7F11E0
Output:  rgba( 127, 17, 224, 1 )
Input:     #1C14B0
Output: rgba( 28, 20, 176, 1 )

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In this article, we will discuss various ways to convert Hex to RGBA using Javascript.

Use parseInt and String.substring methods
Using array destructuring and regular expressions

Use ParseInt and String.substring methods

The parseInt() function accepts two parameters: a string representing a number and a number representing the base. It then converts the string to an integer in the specified base and returns the result.

String.substring method is used to extract some parts of a string by getting the start and end positions.

To convert HEX to RGBA we use the following steps.

Leave # and use the String.substring method to extract a pair of two characters of the hexadecimal string one by one.
After extraction, use the parseInt method to convert each pair to an integer. We know that these pairs are hex codes, so we need to pass 16 to the second argument of parseInt.
After converting each pair of hexadecimal codes to integers, concatenate them into RGBA format.

Example

In this example, we convert the hex code to RGBA.

<!DOCTYPE html>
<html>
<head>
   <title>Convert Hex to RGBA value using JavaScript</title>
</head>
<body>
   <h3>Converting Hex to RGBA value parseInt() and String.substring() methods</h3>
   <p id="input"> Hex Value: </p>
   <p id="output"> RGBA Value: </p>
   <script>
      let hex = "#7F11E0";
      let opacity = "1";
      // Convert each hex character pair into an integer
      let red = parseInt(hex.substring(1, 3), 16);
      let green = parseInt(hex.substring(3, 5), 16);
      let blue = parseInt(hex.substring(5, 7), 16);
      
      // Concatenate these codes into proper RGBA format
      let rgba  = ` rgba(${red}, ${green}, ${blue}, ${opacity})`
      
      // Get input and output fields
      let inp = document.getElementById("input");
      let opt = document.getElementById("output");
      
      // Print the values
      inp.innerHTML += hex;
      opt.innerText += rgba;
   </script>
</body>
</html>

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Use Array.map() and String.match() methods

Javascript Array The map() method creates a new array containing the results of calling the provided function on each element in the array.

String.match method is used to retrieve matches when matching a string with a regular expression.

To convert HEX to RGBA we use the following steps.

Use the /\w\w/g regular expression and the String.match method to match every sequence of two consecutive alphanumeric characters of a hexadecimal string.
You will get three pairs of alphanumeric characters in an array and convert these characters to integers using Array.map and parseInt methods.

Example

In this example, we convert the hex code to RGBA.

<!DOCTYPE html>
<html>
<head>
   <title>Converting Hex to RGBA value using JavaScript</title>
</head>
<body>
   <h3>Convert Hex to RGBA value using Array.map() and String.match() methods</h3>
   <p id="input"> Hex: </p>
   <p id="output"> RGBA: </p>
   <script>
      let hex = "#7F11E0";
      let opacity = "1";
      
      // Use a regular expression to extract the individual color values from the hex string
      let values = hex.match(/\w\w/g);
      
      // Convert the hex color values to decimal values using parseInt() and store them in r, g, and b
      let [r, g, b] = values.map((k) => parseInt(k, 16)) 
      
      // Create the rgba string using the decimal values and opacity
      let rgba = ` rgba( ${r}, ${g}, ${b}, ${opacity} )`
      
      // Get input and output fields
      let inp = document.getElementById("input");
      let opt = document.getElementById("output");
      
      // Print the values
      inp.innerHTML += hex;
      opt.innerText += rgba;      
   </script>
</body>
</html>

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