JSFiddle - React, Tailwind, and code Playground

JavaScript

var firstTerm = 0, secondTerm = 1, resultTerm = 0,summ = 0;

while(resultTerm <= 4000000){
    resultTerm = firstTerm + secondTerm;
    firstTerm = secondTerm;
    secondTerm = resultTerm;
    if(resultTerm % 2 == 0){
        summ += resultTerm;
    }
};
console.log(summ);