Numbers in JavaScript are stored as standard 64-bit floating-point numbers. This means that you can write numbers with the decimal point anywhere and things will usually just work.
You use +, -, *, / for the usual arithmetic operations. Note that, as you were shown in school, multiplication and division happen before addition and subtraction, so 7 + 2 * 10 is 27 (not 90).
Text in JavaScript (called strings of characters) can be enclosed in single quotes (apostrophes) or double-quotes. I usually use single quotes for most things (because they’re less obtrusive) and double-quotes for full sentences (where you might want to put an apostrophe in the text).
Strings must be written on a single line. If you need to put a line break in a string, you can use \n (“newline”). If you need to insert the quote character that you’re using, you can write \' or \".
Modern JavaScript has another form of strings which they call template literals. These are enclosed in backtick (grave accent) characters: `. They can contain line breaks. They also allow you to insert variables or computed values by writing ${code} (this is called expression interpolation). And as you might guess, if you need to insert a backtick, you put a backslash before it.
True and false are called booleans, after the short-lived 19th-century mathematician George Boole, who did some of the early work on logical operators (AND, OR, NOT, and so on).
Like many other languages, JavaScript uses && for AND, || for OR and ! for NOT. Like the math operators, these have a certain precedence. ! happens before &&, which happens before ||. But you probably won’t remember that (I often don’t) so use parentheses if you’re writing complex conditions.
Conditional operators are === and !== (equal and not-equal), <, >, <=, >= (but not =< or =>, the = must be at the end).
JavaScript also has “approximate” equal and not-equal (== and !=), but they do a complex type conversion process which sometimes leads to unexpected results, so you’re better off using the exact equality operators in the previous paragraph.