Check if a jquery has been loaded or not
Given a document, The task is to determine whether JQuery has been loaded or not, If not then load it dynamically using JavaScript. Below are the examples to check:
Approach:
- First check if it is loaded.
- If not loaded then load it dynamically, create a script element and add properties like(type, src) to it and then finally append it at the end, inside of the head element.
Example 1: In this example, the JQuery is already loaded so message ‘Script already loaded!’ prints on screen.
<!DOCTYPE HTML><html> <head> <title> JavaScript | Check if jquery has been loaded, If not then load. </title> <script src= </script></head> <body style="text-align:center;" id="body"> <h1 style="color:green;"> GeeksForGeeks </h1> <p id="GFG_UP" style="font-size: 19px; font-weight: bold;"> </p> <button onClick="GFG_Fun()"> click here </button> <p id="GFG_DOWN" style="color: green; font-size: 24px; font-weight: bold;"> </p> <script> var up = document.getElementById('GFG_UP'); var down = document.getElementById('GFG_DOWN'); up.innerHTML = "Click on button to check whether JQuery is loaded"; function GFG_Fun() { if (!window.jQuery) { var el = document.createElement('script'); el.type = "text/javascript"; el.src = document.getElementsByTagName( 'head')[0].appendChild(el); down.innerHTML = "Script loaded successfully!"; } else { down.innerHTML = "Script already loaded!"; } } </script></body> </html> |
Output:
- Before clicking on the button:
- After clicking on the button:
Example 2: The src attribute of script element is changed to sc. In this example, the JQuery is not loaded so message ‘Script loaded successfully!’ prints on screen after successful loading.
<!DOCTYPE HTML><html> <head> <title> JavaScript | Check if jquery has been loaded, If not then load. </title> <script sc= </script></head> <body style="text-align:center;" id="body"> <h1 style="color:green;"> GeeksForGeeks </h1> <p id="GFG_UP" style="font-size: 19px; font-weight: bold;"> </p> <button onClick="GFG_Fun()"> click here </button> <p id="GFG_DOWN" style="color: green; font-size: 24px; font-weight: bold;"> </p> <script> var up = document.getElementById('GFG_UP'); var down = document.getElementById('GFG_DOWN'); up.innerHTML = "Click on button to check whether JQuery is loaded"; function GFG_Fun() { if (!window.jQuery) { var el = document.createElement('script'); el.type = "text/javascript"; el.src = document.getElementsByTagName( 'head')[0].appendChild(el); down.innerHTML = "Script loaded successfully!"; } else { down.innerHTML = "Script already loaded!"; } } </script></body> </html> |
Output:
- Before clicking on the button:
- After clicking on the button:
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