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Have you ever encountered the error “Uncaught SyntaxError: Identifier ‘a’ has already been declared” in your javascript code? Despite the error’s simplicity, it can be difficult to diagnose and fix. In this blog, we’ll discuss some quick strategies for resolving it.
When does this error “Uncaught SyntaxError: Identifier ‘a’ has already been declared” occur?
When trying to run a simple program, you may get the following error.
Uncaught SyntaxError: Identifier 'a' has already been declared
Here’s a sample of the code:
var a = 1;
if(true){
function a(){};
var a = 10;
}
console.log(a)
What causes error?
If you encounter the above situation, it is most likely due to one of the following reasons:
– Duplicate declaration
– Do not use var to declare a in block scope
Also you should know that, declarations of functions inside if blocks were not valid in ES5, therefore they will be able to use the ES6 semantics with more stringent rules for declarations that are duplicated.
How to deal with error?
Here are some solutions for you to find the fastest way to deal with the error:
Option 1
You can Assign a to the value of a function, here is an example:
var a;
a = function(){}; // now a holds the value as a function
console.log(a); // output : f a(){}
a = 1; // a is a var that holds value 1
a = 10; // a is a var that holds value 10
console.log(a); // output : 10
Or use “let” like below:
var a;
a = 1;
if(true) {
a = function() {};
let a;
a = 10;
}
console.log(a); // output : f a(){}
Option 2
You didn’t utilize var when declaring ‘a’ in the block scope. You’ll need to utilize a function declaration that takes block scopes into account (Or else, as in ES5 strict mode, the code will be totally invalid.). The same is true here. The block’s function declaration utilizes ES6 declaration semantics (such as let or const), which prevents redeclarations.
Option 3
You can make use of the information provided below.
var a;
a = 1;
if(true) {
a = function() {};
let a; // The function declaration in the block uses ES6 declaration semantics (like let or const), which does not allow re-declarations.
var a; // throws Uncaught SyntaxError: Identifier 'a' has already been declared
a = 10;
}
console.log(a);
Conclusion
We hope you enjoyed our article about Java. With this knowledge, we know that you can fix your “Uncaught SyntaxError: Identifier ‘a’ has already been declared” error quickly by following these steps! If you still have any other questions about fixing this syntax error, please leave a comment below. Thank you for reading!
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