In this tutorial, we are going to learn about how to solve the TypeError: toLowerCase is not a function in JavaScript
When we use a ‘toLowerCase()’ method on a value which is not a data type string we will get the following error in our console.
Example:
const value = 8999; console.log(value.toLowerCase());
Output:
“TypeError: value.toLowerCase is not a function
In the example above, we are getting the error because we are using the ‘toLowerCase()’ method on a datetype number, but the toLowerCase() is not available on the number datatype.
To solve the “TypeError: toLowerCase is not a function”, make sure to call the toLowerCase() method on a data type string or convert the number to string before calling the toLowerCase() method on it.
Here is an example:
const value = 8999; const result = value.toString().toLowerCase(); console.log(result);
Output:
In the example above, we first converted the given value to a string using the toString() method, then we called a toLowerCase() method on it.
Note: The ‘toLowerCase()’ method creates a new string with the values that passes the test condition.
Type checking
To avoid the run time errors, we can also check the given datatype is a string or not before calling the toLowerCase() method on it.
Here is an example:
const value = 8999; if(typeof value === ‘string’){ console.log(value.toLowerCase()); }else{ console.log(‘Given value is not a string’); }
Conclusion
The “toLowerCase is not a function” error occurs, when we call a toLowerCase() method on a value which is not a string. To solve the error, convert the value to an string before calling the toLowerCase() method on it or make sure to use the toLowerCase() method on a valid strings.
