JSFiddle - React, Tailwind, and code Playground

by TheDiamondDoge

JavaScript

function sumStrings(a,b) { 
  let reverseA = a.split("").reverse();
  let reverseB = b.split("").reverse();
  let maxLength = Math.max(reverseA.length, reverseB.length);
  let resultArray = [];
  
  let dec = 0;
  for (let i = 0; i < maxLength; i++) {
  	let numA = Number(reverseA[i] || 0);
  	let numB = Number(reverseB[i] || 0); 
    
   	let sum = numA + numB + dec;
    dec = 0;
    
		resultArray.push(sum % 10);
    dec = Math.floor(sum / 10);
  }
  
  if (dec) {
  	resultArray.push(dec);
  }
  
  return resultArray.reverse().join("").replace(/^0+/g, "");
}

console.log(sumStrings('123','00456'))