Beginner’s Guide to Javascript You Should Know For AdWords Scripts

I’ve heard from a few readers that the posts on this blog have inspired them to learn to code. That’s awesome! But I’ve also heard from a few that say they have run into trouble getting through many of the Javascript tutorials out there since they deal mostly with Javascript for web design or Node.js.

So this post is going to attempt to get someone up to speed with Javascript enough that they can at least walk through most of the code I post here and make changes when needed. Also, I aim to at least help you know what to Google when you get stuck.

A few caveats. Is this meant to be a replacement for a full coding class? No. Will I be making generalizations and over-simplifying some extremely complex topics? Yes. Are there mistakes in this? Probably. If you find one, let me know.

/*********************************
* Intro to Javascript For AdWords Scripts
* Version 1.0
* Created By: Russ Savage
* FreeAdWordsScripts.com
*********************************/
function main() {
  // This is a comment. AdWords Scripts ignores this
  /* Here is another way to comment
     that can be used when you need
     to comment multiple lines */
  
  // The main function tells AdWords where to start. You always need
  // at least a main function in your script.
  
  // Let's start with some variables (or primatives)
  // More info on Javascript variables can be found:
  // http://www.tutorialspoint.com/javascript/javascript_variables.htm
  var clubName="Fight Club"; // declared with single quotes
  var rule1 = "Don't talk about fight club."; // or double quotes if needed
  var members = 12; // a number, no quotes
  var dues = 3.50; // also a number
  var isAcceptingNewMembers = true; // a boolean, for yes or no answers
  
  // When you need to store multiple values, consider an Array
  // More detailed intro to Arrays can be found here:
  // http://www.w3schools.com/js/js_obj_array.asp
  var memberNames = ['brad','edward','robert'];
  // Which you can access the values with an index
  var coolestMember = memberNames[0]; // pronounced member names sub zero
  // 0 is the index of the first element of the array, 1 for the second, etc.
  // We can use the length property of an array to find out how big it is.
  var numberOfMembers = memberNames.length; // this will be 3
  var dailyFights = numberOfMembers*2; // star ( * ) is an operator for multiply
  // so the total number of fights is 6.
  // More on operators can be found here:
  // http://web.eecs.umich.edu/~bartlett/jsops.html
  
  // If you want to group multiple variables together, you can using an Object.
  // An Object is simply a grouping of common variables (and other stuff we'll see later)
  var FightClub = { // The curly brace says group these things together. there is another one at the end.
    clubName : 'The Fight Club', // a string variable. In an Object, we use : instead of = for assignment
    rules : ["Don't talk about fight club.",  // each variable is separated by a comma, instead of a semi-colon
             'Do not talk about fight club.'],
    memberNames : ['brad','eddy','robert','phil','dave'],
    dues : 3.50, 
    foundedYear : 1999
  };
  // Now to access the variables inside the object, we use the dot
  Logger.log(FightClub.clubName); // prints The Fight Club
  Logger.log(FightClub.memberNames[0]); // prints brad
  
  // Objects are one of the most important concepts of Javascript and they will come back
  // again and again a little later. More details can be found here:
  // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Working_with_Objects
  
  // Sidebar: Why do I use camelCase for variable names? Technically
  // I could 
  var UsEWhaTevERIwanteD = 'but camelCase is easier to read';
  // and conforms to the style guide that Google recommends:
  // https://google-styleguide.googlecode.com/svn/trunk/javascriptguide.xml#Naming
  // Follow the style guide. It helps others read your code.
  
  // If statements (or control statements) allow you to split your code path if needed
  if(numberOfMembers > 10) { // if we have more than 10 members
    dues += 1.00; // increase the dues, 
    // plus equals (+=) says "add the value on the right to the value on the left"
  } else { // otherwise
    dues -= 1.00; // decrease the dues
    // there are also -=, *= (multiply), /= (divide by), and %= (modulo equals)
  }
  // Comparison operators like >, = allow you to compare values
  // They return true or false, always
  // Notice the double and triple equal signs. That's not a typo. More info can be found at:
  // http://www.impressivewebs.com/why-use-triple-equals-javascipt/
  
  // You can also have multiple if statements and multiple things to test
  if(dues > 5) { // if dues are over $5
    dailyFights++; // increase the fights
  } else if(dues > 2 && dues