Sometimes, we may run into the ‘ReferenceError: "x" is not defined’ when we’re developing JavaScript apps.
In this article, we’ll look at how to fix the ‘ReferenceError: "x" is not defined’ when we’re developing JavaScript apps.
Fix the ‘ReferenceError: "x" is not defined’ When Developing JavaScript Apps
To fix the ‘ReferenceError: "x" is not defined’ when we’re developing JavaScript apps, we should make sure that we do operations on variables that have already been declared.
We should also make sure the variable is available in the scope that we want to do the operation to.
For instance, instead of writing:
foo.substring(1);
which will throw the error since foo isn’t defined before we call substring, we write:
const foo = 'bar';
foo.substring(1)
to declare foo before calling substring.
We should also make sure the variable is actually available in the given scope before we do any operation with it.
For instance, we write:
const add = () =>{
const num1 = 2,
num2 = 3;
return num1 + num2;
}
console.log(num1);
which will throw the error since num1 is only available in the add function.
Instead, we write:
const add = () => {
const num1 = 2,
num2 = 3;
console.log(num1);
return num1 + num2;
};
to log the num1 value since it’s available in the add function.
Conclusion
To fix the ‘ReferenceError: "x" is not defined’ when we’re developing JavaScript apps, we should make sure that we do operations on variables that have already been declared.
We should also make sure the variable is available in the scope that we want to do the operation to.
