Replace Uppercase and Lowercase in a String using JavaScript

We are required to write a JavaScript function that takes in a string and constructs a new string with all the uppercase characters converted to lowercase and all the lowercase characters converted to uppercase.

Let’s write the code for this function −

Example

Following is the code −

const str = 'The Case OF tHis StrinG Will Be FLiPped';
const isUpperCase = char => char.charCodeAt(0) >= 65 && char.charCodeAt(0)
<= 90;
const isLowerCase = char => char.charCodeAt(0) >= 97 &&
char.charCodeAt(0) <= 122;
const flipCase = str => {
   let newStr = '';
   const margin = 32;
   for(let i = 0; i < str.length; i++){
      const curr = str[i];
      if(isLowerCase(curr)){
         newStr += String.fromCharCode(curr.charCodeAt(0) - margin);
      }else if(isUpperCase(curr)){
         newStr += String.fromCharCode(curr.charCodeAt(0) + margin);
      }else{
         newStr += curr;
      };
   };
   return newStr;
};
console.log(flipCase(str));

Output

The output in the console: −

tHE cASE of ThIS sTRINg wILL bE flIpPED