Syntax

Comma (,)

evaluate each operands (left to right) and returns the value of the last operand

Opional chaining (?.)

https://www.typescriptlang.org/docs/handbook/release-notes/typescript-3-7.html#optional-chaining

Immediately stop running expression and return undefined, if encountered null or undefined

foo?.bar?.baz

array?.[0]

log?.(`log or not log`);

Nullish Coalescing (??)

let x = foo ?? bar(); // equals to the much longer version below

let x = foo !== null && foo !== undefined ? foo : bar();

Non-null assertion operator (!.)

let s = e!.name; // Assert that e is non-null and access name

Spread syntax (...obj)

'obj' being an array, expand the expression (i.e. obj) in places where multiple arguments (function calls) or multiple elements (array literals) are expected

for (basic version)

for (statement 1; statement 2; statement 3) {

  // code block to be executed

}

for/in - iterate through enumerable properties of an object

var person = {fname:"John", lname:"Doe", age:25};

for (x in person) {

  // iterate object keys

}

for / of & iterator protocol

an iterator is object with:

• next() - return an object with at least two properties, {done:boolean, value:any}

an iterable is object implement the @@iterator method, that is:

• have a property with a Symbol.iterator key
• the property is an iterator

A generator is an iterator

for/of - loops through iterable objects:

• arrays - through members
• string - through each character
• Map (standard built-in object) - elements in insertion order
• other iterables, including generators

Example

for (const [key, value] of Object.entries(object1)) {

}

while & do/while

same as Java