In the abstract, rest assured that a problem was solved.

JavaScript One Page

JavaScript operates. This one page presents points to bear in mind when entering a technical exam.

Concepts

let carName; // undefined
Variables defined with var are hoisted to the top, meaning you can use the variable before it is declared.
Use const when you declare:

A new Array
A new Object
A new Function
A new RegExp

Iterables must implement the Symbol.iterator method. String, Array, TypedArray, Map and Set are all iterables. Their prototype objects have a Symbol.iterator method.

Methods

const myArray = text.split(" ", 3);
let result = text.slice(0, 5);
let result = text.substring(1, 4);
let result = text.substr(1, 4);
x.toString()
(123).toString()
(100 + 23).toString()
Number() Returns a number, converted from its argument
parseFloat() Parses a string and returns a floating point number
parseInt() Parses a string and returns an integer
typeof "John Doe"
typeof (3 + 4)

Loops

for (let i = 0; i < 27; i++) {
    console.log("i: ", i);
}
        
for (variable of iterable) {
    // code block to be executed
} 

const letters = new Set(["a","b","c"]);

for (const x of letters) {
    // code block to be executed
}

Conditionals

if ( number <= 1 )  // base case
    return 1;
else
    return number * factorial( number - 1 );

if ( number <= 1 )  // base case { 
    return 1; }          
else {            
    return number * factorial( number - 1 ); }

DOM

target = window.prompt("Factorial to what integer?", "1000");

document.getElementById("demo").innerHTML = "Hello JavaScript";
document.getElementById("demo").style.fontSize = "35px";
document.getElementById("demo").style.display = "none";

window.addEventListener( "load", start, false );
// "event", function, capture flag

Add Style Classes

const element = document.getElementById("myDIV");
element.classList.add("styleOne");
element.classList.add("styleTwo");