Error : missing new prefix when invoking a constructor

Question

I am trying to create a function in node.js. The following is relevant code, it gives me error when i call function.

function ReplacePlaceholders() {
            return 'success';
          }      



  exports.sendMailMsg = function (templateName, receiverEmail, dataPlaceholders) {

        ReplacePlaceholders();
}

Answer 1

In node.js, function names are camel cased, and should start with a lowercase character. Starting a function with an uppercase character tells JSHint to consider the function a constructor rather than a method.

This is actually an error being generated by JSHint, but the code will run correctly. The option in JSHint, newcap, which causes this error is actually depreciated, and disabling it is recommended.

The relevant info as to why this option is even in JSHint:

This option requires you to capitalize names of constructor functions. Capitalizing functions that are intended to be used with new operator is just a convention that helps programmers to visually distinguish constructor functions from other types of functions to help spot mistakes when using this.

Not doing so won't break your code in any browsers or environments but it will be a bit harder to figure out—by reading the code—if the function was supposed to be used with or without new. And this is important because when the function that was intended to be used with new is used without it, this will point to the global object instead of a new object.

Answer 2

The error message you mention is a JSHint error message, not a runtime error. There is a discussion of it here:

jshint expects the new 'prefix' for functions

JSHint expects functions that start with a capital letter to be object definitions. You can ignore the error, disable it in JSHint, or rename your function so that it starts with a lower-case letter.