The primitive types in Typescript are boolean, number and string. All of them are immutable and they are very optimized internally. number includes both integers and floating point numbers and the internal format is the IEEE 754 64-bit double precision real number (double in C, Java, etc).

Quotes

Typescript has 3 types of quotes:

• Single quotes ('): To delimit strings.
• Double quotes ("): Equivalent to the single quotes.
• Backticks (`): They enable multiline strings and interpolation.

Multiline strings allow line breaks:

let message = `This message 
occupies more
than one
line`;

Interpolation evaluates expressions within ${} delimiters:

let first = "James", last = "Bond";
console.log(`My first is ${last}, ${first} ${last})

Special values

undefined is used to mark variables that have never been initialized. It is the value that variables have when they weren't assigned on declaration. (It is possible to assign undefined after the definition but very misleading.)

null is used to tell that a variable is empty. It is more explicit than undefined since it has te be assigned.

Conversions

You can convert between these types with Number, Boolean or String.

Conversions to boolean:

Boolean(0); // (is it different than 0?) -> false
Boolean(7); // (is it different than 0?) -> true
Boolean(''); // (string has characters?) -> false
Boolean('sdfsd'); // (string has characters?)  -> true
Boolean(null); // (is there anything?) -> false
Boolean(undefined); // (is there anything?) -> false

Conversions to number:

Number('123'); // parse an integer --> 123
Number('abc'); // not an integer   --> NaN
Number(true); // --> 1
Number(false); // --> 0
Number(null); // (something empty as a number?) --> 0
Number(undefined); // (something unknown as a number?) --> NaN

Conversions to string:

String(true); // 'true'
String(false); // 'false'
String(0); // '0'
String(123); // '123'
String(null); // 'null'
String(undefined); // 'undefined'

typeof

You can obtain the type of any value with typeof: