Understanding and Working with ES6 String Methods in JavaScript

In JavaScript, ES6 (also known as ECMAScript 2015) introduced a range of new and simplified methods for string manipulation. The question above particularly refers to the replacement of a common JavaScript operation: checking if a specific string is present within another string.

Before ES6, developers had to use indexOf(). This method returns the index of where the substring starts in the string, or -1 if the string is not found. This often resulted in code like the following:

let some_text = "some string";
if(some_text.indexOf('str') != -1){
  return true;
}

This piece of code is checking if 'str' exists in some_text. If indexOf() does not return -1, it means 'str' exists in some_text, hence true is returned. Although it works perfectly fine, ES6 introduced a more readable and intuitive method for this kind of operation: includes().

Usage of includes()

The correct answer to the question is some_text.includes('str');. The includes() method simply checks if the string includes the specified string or not. It returns a boolean value — true if the string is found, and false if not.

Here is how you can use it:

let some_text = "some string";
console.log(some_text.includes('str')); // Outputs: true

With includes(), the code becomes much more readable, especially to people new to JavaScript. The method clearly states its purpose, making the code easier to understand without needing comments.

Best Practices and Additional Insights

It is always good to utilize new methods and syntax that come with updates to a language. This not only makes your code more readable but also keeps it up-to-date with modern standards.

It's also important to understand the difference between includes() and other similar string methods in ES6 like startsWith() and endsWith(). These are not interchangeable and each serves a different purpose.

startsWith() checks if the string begins with specified characters, while endsWith() checks if the string ends with specified characters. So, understanding each of these methods and their unique functionalities is key to efficient and effective string operation in JavaScript.

Similarly, repeat() is another ES6 method that isn't interchangeable with the above three. It returns a new string which is an existing string repeated a certain number of times.

So in conclusion, includes() is an ES6 string method that simplifies checking if a string includes a specific substring, making the code tidier and more intuitive.