Javascript

this

in Javascript what this is based on how you invoke the function

functions

new

function Foo() {
    this.bar = "baz";
    console.log(this);
}
var f = new Foo();
console.log(f.bar);

Learning Resources

MDN Javascript Guide
Javascript Garden
quiz.typeofnan.dev — Learn JavaScript fundamentals through fun and challenging quizzes

Logical operators

MDN: Logical Operators

.map

.reduce