Module 1 - Day 2

JS Functions basics

Contents

JS | Functions basics: declaration invocation default parameters arrow syntax for anonimous functions

Functions

At the nomenclature level, there are:

• Nominal functions: they have declaration and invocation, with high reusability.

  function sayHi(name){
    console.log(`Hello, ${name}!`)
  }

• Anonymous functions: no declaration, only invocation. Used in a single context.

  names.forEach(function(elm) => {
     console.log(`Hello, ${elm}!`)
  })

At the structure level, there are:

• Function statement: they have the reserved word function, parentheses for their parameters and block:

  function getTotals(subtotal, tax){
    return subtotal + tax
  }

• Arrow function: they lack the reserved word function, the parenthesis in their parameters can be omitted in front of a single parameter, and they have an arrow before the opening of their block (block can be omitted in functions of a single instruction).

  const getTotals = (subtotal, tax) => subtotal + tax

Functions can receive arguments in the form of parameters, and return data. Concerning their return:

• They can only return a single value, or undefined if they lack a return.
• A return in a function means stopping its execution.
• Arrow functions without a block have a return by default.

For variable scoping purposes:

• Variables declared inside a block or function are called local or private, accessible only within that context.
• Variables declared outside any block or function are called global or public, accessible from anywhere in the script.