JSFiddle - React, Tailwind, and code Playground

JavaScript

// charAt,slice and index method of javaScript

function upTo(number) {
    var result = [];
    for(var i = 0; i <= number; i++) {
        result[i] = i;
    }
    return result;
}

alert(upTo(4));

var string = "1111111111111111111F";
// check F at the end
if(string.charAt(19) == 'F') {
    alert("hai F hai end main");
}

// check particular String on given String
var string2 = "we are all son of God";
// check 'God' at the last
if(string2.slice(18,21) === 'God') {
    alert("hai last main God hai")
}

var string3 = "1111111111111111111F";
alert(string3.indexOf("F"))