Types
Numbers
JavaScript uses 64 bits to store number values
Fractional numbers
console.log(9.81)Scientific notation
console.log(2.998e8)Special Numbers
-
Infinity
Infinity and -Infinity represent positive and negative infinities
console.log(Infinity - 1) console.log(Infinity + 1) console.log(-Infinity - 1) console.log(-Infinity + 1) -
NaN
Not a number. The returned result if you try to do mathematical nonsense
console.log(0/0) console.log(Infinity - Infinity)
Strings
Following are acceptable strings
console.log(`Down on the sea`)
console.log("Lie on the ocean")
console.log('Float on the ocean')Backslash escapes characters
console.log("This is the first line\nAnd this is the second")
console.log("A newline character is written like \"\\n\".")Backtick quoted strings (template literals) can span lines and also embed other values. ${} in a template literal will be computed and converted to a string
console.log(`This is a
backtick quotes string`)
console.log(`half of 100 is ${100 / 2}`)Boolean
console.log(3 > 2)
console.log(3 < 2)Strings can also be compared
console.log("Aardvark" < "Zoroaster")Uppercase characters are always less than lower case characters, so “Z” < “a”. Non alphabetic characters are less than alphabetic characters
console.log("Zebra" < "aardvark")
console.log("!" < "aardvark")
console.log("!" < "Zebra")
console.log("3" < "Zebra")
console.log("!" < "3")Empty values
There are two special empty values, null & undefined that denote the absence of any meaningful value. They can be used interchangeably and are an accident of JavaScripts design.
console.log(null == undefined);ES6
Symbols
They are tokens that serve as unique IDs. You create symbols via the factory function Symbol() (which is loosely similar to String returning strings if called as a function):
const symbol1 = Symbol();Add a description
const tralala = Symbol('tralala')
console.log(tralala) // Symbol(tralala)Convert to string
const tralala = Symbol('tralala')
console.log(String(tralala)) // `Symbol(tralala)`Every Symbol is unique
console.log(Symbol() === Symbol()) // falseProperty keys
const KEY = Symbol();
const obj = {};
obj[KEY] = 123;
console.log(obj[KEY]); // 123const FOO = Symbol();
const obj = {
[FOO]() {
return 'bar';
}
};
console.log(obj[FOO]()); // bar