What's lambda in Javascript?

Answer 1

it is short writings in coding
here is a good example for you to check
https://code.sololearn.com/WAlySl61dQKS/?ref=app

Answer 2

const isEven = x => x % 2 === 0

Answer 3

JavaScript calls them closures or even just anonymous functions. They're just functions used where you would normally put a variable's value.

Traditional syntax:
var a = function () {
console.log('hello');
};

There are a couple of new syntaxes allowed in ES6 (one shown by A_hook), but they treat some variables (like `this`) a little differently.