JSFiddle - React, Tailwind, and code Playground

JavaScript

function titleCase(str) {
    var strAr = str.toLowerCase().split(' ');
    for (var i = 0; i < strAr.length; i++) {
        strAr[i] = strAr[i].charAt(0).toUpperCase() + strAr[i].slice(1);
    }
    return strAr.join(' ');
}

alert(titleCase('This is a simple test.'));