function getStyle1(id){
    if ((typeof id == "string") && (id)){
        let myElement = document.getElementById(id);
        if (myElement){ // null check
            return myElement.style;
        }
    }
}
function getStyle2(id){
    // input VALIDATION
    if ((typeof id != "string") || (!id)){
        return undefined;
    }
    // algorithm
    let output;
    let myElement = document.getElementById(id);
    if (myElement){ // null check
        output = myElement.style;
    }
    // output
    return output;
}

let a, b;
if ((typeof a == typeof b) && (a == b)){ // a === b
}
if (a == b){ // types do not match ?!
}

console.log(0 == 0);
console.log("0" == 0);
console.log("0" === 0);

console.log(0 != 0);
console.log("0" != 0);
console.log("0" !== 0);

/*
// validation

console.log(isNaN(NaN));
console.log(isFinite(NaN), isFinite(Infinity), isFinite(-Infinity));

let variable = "";
if (variable){
    console.log("True");
} else {
    console.log("False");
}
if (typeof variable != "number"){
    // null? undefined?
    if (variable != null){ // if (variable)
    }
    if (variable != undefined){ // if (variable)
    }
}

// type is object
if (typeof variable == "object"){
    // null? undefined?
}
if ((typeof variable == "object") && (variable)){
    // Ok
}

// type is number
if (typeof variable == "number"){
    // NaN? Infinity?
}
if ((typeof variable == "number") && (isFinite(variable))){
    // Ok
}
*/

/*
// four horsemen of JS
// "niekas", neradau, nėra, tuščia
let myElement = document.getElementById("manoId");
console.log(myElement, typeof myElement);
if (myElement != null){
    let myStyle = myElement.style;
}

// begalybė ("labai labai labai daug")
let bigNumber = 0;
bigNumber = 1 / 0;
console.log(bigNumber, typeof bigNumber);

// ne skaičius (not a number)
let anyNumber = "du" * 2;
console.log(anyNumber, typeof anyNumber);

// neapibrėžta, nepasakyta, nenurodyta
let something;
console.log(something, typeof something);
*/


/*
// operator ? :
let x = 1010;
console.log("Number " + x + " is " + ((x % 2) ? "odd" : "even"));


let output = "Number " + x + " is ";
if (x % 2){
    output += "odd";
} else {
    output += "even";
}
console.log(output);
*/