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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