Template Literal / Template Strings: were introduced with ES2015 and allow for creating strings with embedded JavaScript expressions. Within backticks, you can combine “hardcoded” strings with JavaScript expressions inside of ${}.
Call Back: Callback is an asynchronous equivalent for a function. Node makes heavy use of callbacks. All the APIs of Node are written in such a way that they support callbacks. A callback is a function which is called when a task is completed, thus helps in preventing any kind of blocking and a callback function allows other code to run in the meantime.
Function Declarations: Declared functions are not executed immediately. They are "saved for later use", and will be executed later, when they are invoked (called upon). Function Expression: The function above is actually an anonymous function (a function without a name). Functions stored in variables do not need function names. They are always invoked (called) using the variable name.
Arrow Function: Arrow functions allow us to write shorter function syntax. If the function has only one statement, and the statement returns a value, you can remove the brackets and the return keyword and you can skip the parentheses as well (one parameter is there). If you have parameters, you pass them inside the parentheses.
Array Function:
Destructuring
Spread operator: It allows an alterable to expand in places where 0+ arguments are expected. It is mostly used in the variable array where there is more than 1 values are expected. It allows us the privilege to obtain a list of parameters from an array. Syntax of Spread operator is same as Rest parameter but it works completely opposite of it.
Rest parameter: is an improved way to handle function parameter, allowing us to more easily handle various input as parameters in a function. The rest parameter syntax allows us to represent an indefinite number of arguments as an array. With the help of a rest parameter a function can be called with any number of arguments, no matter how it was defined.