SyntaxError: expected expression, got '<', what does that mean?

问题:

I know this is asked a few times on S.O.

but none of the answers seem to match my situation . So, I have a a basic Html page which tries to use an external JS. The JS file tries to change the content of a paragraph defined in the HTML on a button click, but does not seem to work.

I see the following errors in console :

1)SyntaxError: expected expression, got '<'

2)ReferenceError: change is not defined

JSFiddle showing exact source?(except that & tags are removed as jsfiddle - http://jsfiddle.net/p9ko4yde/

HTML Code :

<h1> Numbers with external script:) </h1> <p id="number">1</p> <button type="button" onclick="change()">Toggle between 1 and 2</button>  <script src="myScript.js"></script>    </body> </html> 

JS Code :

<script type="text/javascript">     function change(){         var number = document.getElementById('number').innerHTML;         if(number == '1'){             document.getElementById('number').innerHTML='2';         }         else{             document.getElementById('number').innerHTML='1';         }     } </script> 

File Structure is as below:

回答1:

You don't need the <script> tags when in an external .js file. Use these tags to embed a script inside HTML only.

回答2:

The syntax error is because you have <script> tags in your JS file. When you put JavaScript in its own file like that, you don't need to surround it with script tags; that's HTML, and this is a JavaScript file.

The reference error is happening because, due to the syntax error, the JS file isn't executing correctly and so the change function never got created -- fixing the syntax error should also resolve this.

回答3:

In a js file, you do not use the HTML to declare that it is a js file. So, you can drop the script tag in myScript and change it to this :

function change(){     var number = document.getElementById('number').innerHTML;     if(number == '1'){         document.getElementById('number').innerHTML='2';     }     else{         document.getElementById('number').innerHTML='1';     } } 

回答4:

Sometimes this error happens when the Javascript referenced file doesn't exist. Make sure that the file name is correct and you have the file in place. I know your problem is solved but maybe this answer solves someone else's :)

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