How to tell if a <script> tag failed to load?

The problem is to identify whether the passed script loaded successfully or not using JavaScript. There are two methods which are discussed below:

Approach 1:

  • Set a variable loaded = false.
  • Pass the URL of the JavaScript file in the <script> tag.
  • Set the onload parameter, if script loaded set loaded = true.

Example:This example illustrate the approach discussed above.



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<!DOCTYPE HTML> 
<html> 
  
<head> 
    <title> 
        How to tell if a script tag failed
        to load in JavaScript ?
    </title>
      
    <script>
        var loaded = false;
    </script>
      
    <script src=
"https://ajax.googleapis.com/ajax/libs/jquery/3.4.1/jquery.min.js"
                onload="loaded=true;" >
    </script>
</head> 
  
<body style = "text-align:center;"> 
      
    <h1 style = "color:green;"> 
        GeeksgorGeeks 
    </h1>
      
    <p id = "GFG_UP" style = 
        "font-size: 15px; font-weight: bold;">
    </p>
      
    <button onclick = "gfg_Run()"> 
        Click here
    </button>
      
    <p id = "GFG_DOWN" style =
        "font-size: 23px; font-weight: bold; color: green; ">
    </p>
      
    <script>
        var el_up = document.getElementById("GFG_UP");
        var el_down = document.getElementById("GFG_DOWN");
          
        el_up.innerHTML = "Click on the button to check "
                    + "whether script is loaded or not."; 
          
        function gfg_Run() {
            if(loaded) {
                el_down.innerHTML = "Loaded Successfully!";
            }
            else {
                el_down.innerHTML = "Not loaded!";
            }
        }         
    </script> 
</body> 
  
</html>

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Output:


    

  • Before clicking on the button:
    

    • 

  • After clicking on the button:
    

    • 



Approach 2:


    

  • Set a variable loaded = false.
    • 

  • Pass the URL of JavaScript file in a <script> tag.
    • 

  • Set the onload parameter, Trigger alert if script loaded.
    • 

  • If not then check for loaded variable, if it is equal to false, then script not loaded.
    • 



Example: This example follows the approach discussed above.











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<!DOCTYPE HTML>  


<html>  


  


<head>  


    <title>  


        How to tell if a script tag failed 


        to load in JavaScript ? 


    </title> 


      


    <script> 


        var loaded = false; 


    </script> 


      


    <script src="" 


        onload="alert('Script loaded!'); loaded=true;" > 


    </script> 


</head>  


  


<body style = "text-align:center;" id = "body">  


      


    <h1 style = "color:green;" >  


        GeeksforGeeks  


    </h1> 


      


    <p id = "GFG_UP" style =  


            "font-size: 15px; font-weight: bold;"> 


    </p> 


      


    <script> 


        var el_up = document.getElementById("GFG_UP"); 


        el_up.innerHTML = "Click on the refresh button " 


            + "to check whether script is loaded or not."; 


          


        if(!loaded) { 


            alert("Script not loaded!"); 


        } 


    </script>  


</body>  


  


</html> 



















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Output:


    

  • Before clicking on the button:
    

    • 

  • After clicking on the refresh button:
    

    • 




          
          
          
          

            

    

        My Personal Notes
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