JavaScript Compare two sentences word by word and return if they are substring of each other

The idea here is to take two strings as input and return true if one string is a substring of the other, otherwise return false.

For example:

isSubstr('hello', 'hello world') // true
isSubstr('can I use', 'I us') // true  
isSubstr('can', 'no we are') // false

In the function, we check which string is longer and then verify if the shorter string exists as a substring within the longer one.

Syntax

const isSubstr = (first, second) => {
    if (first.length > second.length) {
        return first.includes(second);
    }
    return second.includes(first);
};

Example

const str1 = 'This is a self-driving car.';
const str2 = '-driving c';
const str3 = '-dreving';

const isSubstr = (first, second) => {
    if (first.length > second.length) {
        return first.includes(second);
    }
    return second.includes(first);
};

console.log(isSubstr(str1, str2));
console.log(isSubstr(str1, str3));

Output

true
false

How It Works

The function compares string lengths and uses the includes() method to check if the shorter string exists within the longer one. In the first case, '-driving c' is found in 'This is a self-driving car.', so it returns true. The second case returns false because '-dreving' (with a typo) doesn't exist in the original string.

Additional Examples

console.log(isSubstr('hello', 'hello world'));     // true
console.log(isSubstr('world', 'hello world'));     // true
console.log(isSubstr('javascript', 'java'));       // true
console.log(isSubstr('python', 'javascript'));     // false
console.log(isSubstr('', 'any string'));           // true (empty string)

Output

true
true
true
false
true

Conclusion

This approach efficiently determines substring relationships by comparing lengths first, then using the built-in includes() method. It works bidirectionally, checking if either string contains the other as a substring.