{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Function Expressions in JavaScript\n",
    "\n",
    "I'm currently learning JavaScript, and here are a few things I learned about\n",
    "function expressions in JavaScript ;)\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Anonymous vs Named Functions\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [],
   "source": [
    "// An anonymous function ==> lambda function in Python\n",
    "const clickHandler = function(){\n",
    "    console.log('The user clicked this button.')\n",
    "}"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [],
   "source": [
    "// Named Function \n",
    "const keyHandler = function keyHandler() {\n",
    "    console.log('This is a named function.')\n",
    "}"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "The user clicked this button.\n"
     ]
    }
   ],
   "source": [
    "clickHandler()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "This is a named function.\n"
     ]
    }
   ],
   "source": [
    "keyHandler()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [],
   "source": [
    "const cars = [{make: 'toyota', id: 'Rav4'}, {make: 'tesla', id: 'S'}]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[ \u001b[32m'Rav4'\u001b[39m, \u001b[32m'S'\u001b[39m ]\n"
     ]
    }
   ],
   "source": [
    "// Arrow Function \n",
    "let ids = cars.map(car => car.id)\n",
    "console.log(ids)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "[ \u001b[32m'Rav4'\u001b[39m, \u001b[32m'S'\u001b[39m ]\n"
     ]
    }
   ],
   "source": [
    "// An equivalent named function\n",
    "ids = cars.map(function getId(car){\n",
    "    return car.id\n",
    "})\n",
    "console.log(ids)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Takeaways:\n",
    "\n",
    "- When it comes to\n",
    "  [Arrow functions](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/Arrow_functions),\n",
    "  I often find myself having to carefully read the function body to figure out\n",
    "  what's going on.\n",
    "- IMHO, named functions are the best because they tell us in their name what\n",
    "  they do.\n"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Immediately Invoked Function Expressions (IIFE)\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "metadata": {},
   "outputs": [],
   "source": [
    "const school = 'MIT'"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "CMU\n"
     ]
    }
   ],
   "source": [
    "(function anotherSchool(){\n",
    "    const school = 'CMU'\n",
    "    console.log(school)\n",
    "})()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "MIT\n"
     ]
    }
   ],
   "source": [
    "console.log(school)"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "### Takeaways:\n",
    "\n",
    "- IIFEs are typically used in places in our code where we need to collect a set\n",
    "  of variables and protect them from intruding an outer scope.\n"
   ]
  }
 ],
 "metadata": {
  "author": "Anderson Banihirwe",
  "date": "2021-01-14",
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   "name": "javascript",
   "version": ""
  },
  "tags": "javascript,todayilearned",
  "title": "Function Expressions in JavaScript",
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