JavaScript | Check whether a URL string is absolute or relative

Difficulty Level : Easy
Last Updated : 31 Dec, 2019

The task is to check if the passed URL is absolute or relative. Below are the few approaches:
Approach 1:

Use Regular Expression which checks if the URL contains “//” at a position in the URL .

Example 1: This example uses the approach discussed above.

<!DOCTYPE HTML>
<html>
  
<head>
    <title>
        Test if a URL string is absolute or relative?
    </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 URL = "https://geeksforgeeks.org";
        el_up.innerHTML =
"Click on the button to check if the URL is relative or"+
          " Absolute.<br>URL = '" + URL + "'";
  
        function gfg_Run() {
            var RgExp = new RegExp('^(?:[a-z]+:)?//', 'i');
            if (RgExp.test(URL)) {
                el_down.innerHTML = "This is Absolute URL.";
            } else {
                el_down.innerHTML = "This is Relative URL.";
            }
        }
    </script>
</body>
  
</html>

Output:

Before clicking on the button:
After clicking on the button:

Approach 2:

Use .indexOf() method to get to know if the position of “://” has index greater than 0 or position of “//” has index equal to 0. Both these condition check leads us to the absolute URL.

Example 2: This example uses the approach discussed above.

<!DOCTYPE HTML>
<html>
  
<head>
    <title>
        Test if a URL string is absolute or relative?
    </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 URL = "/myfolder/test.txt";
        el_up.innerHTML = 
"Click on the button to check if the URL is"+
          " relative or Absolute.<br>URL = '" + URL + "'";
  
        function gfg_Run() {
            if (URL.indexOf('://') > 0 || URL.indexOf('//') === 0) {
                el_down.innerHTML = "This is Absolute URL.";
            } else {
                el_down.innerHTML = "This is Relative URL.";
            }
        }
    </script>
</body>
  
</html>

Output:

Before clicking on the button:
After clicking on the button:

My Personal Notes

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JavaScript | Check whether a URL string is absolute or relative