The Case-Sensitivity of JavaScript

The statement "JavaScript is not a case-sensitive language" is false. In fact, JavaScript is a case-sensitive language. This means that it differentiates between upper-case and lower-case letters when interpreting code.

Case-Sensitivity in JavaScript

In JavaScript, variables, function names, and other identifiers must be consistently cased. For example, the variables myVariable, MyVariable and MYVARIABLE would be treated as three separate entities in JavaScript.

let myVariable = 5;
let MyVariable = 10;
let MYVARIABLE = 15;
console.log(myVariable); // Outputs: 5
console.log(MyVariable); // Outputs: 10
console.log(MYVARIABLE); // Outputs: 15

In the above example, each variable, despite having the same spelling, is treated as a separate variable due to the variation in case.

Another impact of JavaScript's case sensitivity comes into play with in-built methods or properties. A good example would be the JavaScript toLowerCase() method. If you incorrectly write this method as toLowercase(), tolowerCase(), or any other case variation, it will result in a JavaScript error, because these are not recognized by the JavaScript engine.

let text = "Hello World";
console.log(text.tolowerCase()); // Incorrect usage, results in a TypeError
console.log(text.toLowerCase()); // Correct usage, outputs: "hello world"

Best Practices and Additional Insights

When scripting in JavaScript, it is considered best practice to stick to a consistent use of case. One common style is camelCase, where the first letter of each word except the first is capitalized (for example, myVariableName). This improves readability, making your code easier to understand for other developers.

Also understand that capitalization in JavaScript can also convey certain conventions or meanings. For instance, it's a commonly accepted convention to only use PascalCase (same as camelCase, but the first letter is capitalized, like MyVariableName) for constructor functions and ES6 classes.

In conclusion, capitalization plays a significant, functional role in a JavaScript application. Its case-sensitive nature shouldn't be overlooked, as doing so may lead to unexpected results and errors in your code. Remembering that JavaScript is indeed a case-sensitive language is hence critical for successful coding.