Program to append two given strings such that, if the concatenation creates a double character then omit one of the characters - JavaScript

We are required to write a JavaScript function that takes in two strings and concatenates the second string to the first string.

If the last character of the first string and the first character of the second string are the same then we have to omit one of those characters. Let’s say the following are our strings in JavaScript −

const str1 = 'Food';
const str2 = 'dog';

Let’s write the code for this function −

const str1 = 'Food';
const str2 = 'dog';
const concatenateStrings = (str1, str2) => {
   const { length: l1 } = str1;
   const { length: l2 } = str2;
   if(str1[l1 - 1] !== str2[0]){
      return str1 + str2;
   const newStr = str2.substr(1, l2 - 1);
   return str1 + newStr;
console.log(concatenateStrings(str1, str2));


Following is the output in the console −