Detect if a string is contained in another string (Javascript)

In JavaScript, you can detect if a string is contained within another string using the includes() method or the indexOf() method.

Here’s an example of using the includes() method:

const str1 = "hello world";
const str2 = "world";

if (str1.includes(str2)) {
  console.log(`${str2} is found in ${str1}`);
} else {
  console.log(`${str2} is not found in ${str1}`);
}

In this example, the includes() method checks whether str2 is found in str1. If it is found, it returns true, otherwise it returns false.

Here’s an example of using the indexOf() method:

const str1 = "hello world";
const str2 = "world";

if (str1.indexOf(str2) !== -1) {
  console.log(`${str2} is found in ${str1}`);
} else {
  console.log(`${str2} is not found in ${str1}`);
}

In this example, the indexOf() method checks whether str2 is found in str1. If it is found, it returns the index of the first occurrence of str2 in str1. If it is not found, it returns -1. We use the !== operator to check if the returned value is not -1, which means str2 is found in str1.

Both includes() and indexOf() are case-sensitive. If you want to perform a case-insensitive search, you can convert both strings to lowercase or uppercase before performing the search. For example:

const str1 = "Hello World";
const str2 = "WORLD";

if (str1.toLowerCase().includes(str2.toLowerCase())) {
  console.log(`${str2} is found in ${str1}`);
} else {
  console.log(`${str2} is not found in ${str1}`);
}

In this example, we convert both str1 and str2 to lowercase using the toLowerCase() method before performing the search.