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Looking for matches in different arrays (Google Apps Script)

I have the following script in Google Apps Script:
for(var i=0; i<lastCode; i++) {
var productCode = prodCodesArr[i];
for(var j=0; j<kelliLastCode; j++) {
var kelliProductCode = kelliCodesArr[j];
if(productCode == kelliProductCode) {
Logger.log('match found')
}
}
}
The 2 arrays are created dynamically. So the idea is (and I know there must be MUCH better ways to do this, but I am pretty new to this so bear with me) that I am setting i to the value of the first product code in one array and then looping through the other array whilst storing the product codes in this one to j. Now, I tried logging:
Logger.log(productCode + ' - ' + kelliProductCode);
And this worked and indeed, there were instances where productCode and kelliProduct code matched.
Yet my if statement above does not pick these up.
Again, I'm sure I've botched this entirely but any help would be greatly appreciated...

What's the point of the check? To determine which of your prodCodesArr items are also in kelliCodesArr? Why not parse kelliCodesArr just once, and then use hash lookups instead of array traversal? This will mean that you don't have to use nested for loops, which will scale very poorly as the inner loop size grows. An example (with some checks for assumptions on my part):
function foo() {
const kelliCodes = getKelliCodesArraySomehow();
const productCodes = getProductCodesArraySomehow();
// If these are 2D arrays, note that for `var a = ['help']; var b = ['help'];`
// `a` is never equal to `b` because they are not the exact same object in memory.
if (kelliCodes.length && Array.isArray(kelliCodes[0])) {
throw new TypeError("This SO answer was predicated on `kelliCodes` and `productCodes` being 1D arrays, but they aren't!");
}
const kelliLookup = kelliCodes.reduce(function (obj, kpc, idx) {
if (typeof kpc === 'object') {
console.log({message: "This SO answer assumed kpc was a string", kpc: kpc});
throw new TypeError("You probably want to store a property of this object, not the whole object");
}
obj[kpc] = idx;
return obj;
}, {});
var productsAlsoInKelliCodes = productCodes.filter(function (pc) {
return kelliLookup.hasOwnProperty(pc);
});
productsAlsoInKelliCodes.forEach(function (pc) {
Logger.log("The index of this product code %s in kelliCodes is %s", pc, kelliLookup[pc]);
});
}
If your ___codes arrays are 2D arrays, you should flatten them before comparison, as comparing an Array instance to another Array instance will always return false, even if they contain the same element primitives--they aren't the exact same Array instance:
References
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Equality_comparisons_and_sameness
Array#forEach
Array#map
In JS, which is faster: Object's "in" operator or Array's indexof?
Javascript: what lookup is faster: array.indexOf vs object hash?
I'm sure there are more.

Something like this might help you to see what's happening:
function compareA(prodCodesArr,kelliCodesArr) {
var html="";
for(var i=0;i<prodCodesArr.length;i++) {
for(var j=0;j<kelliCodesArr.length;j++) {
if(productCodesArr[i]==kelliCodesArr[j]) {
html+=Utilities.formatString('Matched: %s=%s', productCodesArr[i],kelliCodesArr[j]);
}else{
html+=Utilities.formatString('No-Match: %s=%s', productCodesArr[i],kelliCodesArr[j]);
}
}
}
var userInterface=HtmlService.createHtmlOutput(html);
SpreadsheetApp.getUi().showModelessDialog(userInterface, 'Comparing')
}

Counter array in Javascript

I am trying to make two arrays. the unique array can get the elements (no repeats) from the text array, and the counter one can count the frequency of each elements. but something is wrong with the counter one.
var unique_array=new Array();
var counter_array=new Array();
var unique=true;
for (i=0;i<text_array.length;i++){
if (unique_array.length==0){
unique_array.push(text_array[0]);
counter_array.push(1);
}
else if(unique_array.length>0&&unique_array.length<=text_array.length){
for (j=0; j<unique_array.length;j++){
if (text_array[i]==unique_array[j]){
counter_array[j]=counter_array[j]+1;// something wrong with the
alert(counter_array[j]);
var unique=false;
}
}
if (unique==true){
unique_array.push(text_array[i]);
counter_array.push[1];
}
unique=true;
}

You could also simplify the code down using a hashmap and some ES5 higher-order functions:
var text_array = ["a1","a1","a2","a3","a2","a4","a1","a5"];
var counts = {};
text_array.forEach(function(el) {
counts[el] = counts.hasOwnProperty(el) ? counts[el]+1 : 1;
});
var unique_array = Object.keys(counts);
var counter_array=unique_array.map(function(key) { return counts[key]; })

You can do this much more simply using an object. Let the values be the keys of an object, then just increment the count of each property as you go. At the end, you can get an array of the unique keys and their values:
var text_array = ['foo','bar','foo','fum','fum','foo'];
var i = text_array.length;
var obj = {};
while (i--) {
if (obj.hasOwnProperty(text_array[i])) {
obj[text_array[i]]++;
} else {
obj[text_array[i]] = 1;
}
}
console.log('Unique values: ' + Object.keys(obj)); // Unique values: foo,fum,bar
console.log('Value counts: ' + Object.keys(obj).map(function(v){return obj[v]})); // Value counts: 3,2,1
Note that the sorting of counts in the output is purely coincidental.
As Jasvir posted, you can make it pretty concise:
var obj = {};
text_array.forEach(function(v) {
obj.hasOwnProperty(v)? ++obj[v] : obj[v] = 1;
});
But the first example is a bit easier to digest.

I think the approach is what's making it difficult. A hash table / associative array would be much easier to work with.
With a hash table (an object {} in JS), you can store each word in a key and increment the value of the key when you encounter the word again. Then, at the end, just go through the hash table and gather up all the keys which have small values. Those are your unique words.
function get_unique_words(text_array) {
var hash_table, i, unique_words, keys;
hash_table = {};
for(i = 0; i < text_array.length; i++) {
if(hash_table[text_array[i]] === undefined) {
hash_table[text_array[i]] = 1;
} else {
hash_table[text_array[i]]++;
}
}
// go through the hash table and get all the unique words
unique_words = [];
keys = Object.keys(hash_table);
for(i = 0; i < keys.length; i++) {
if(hash_table[keys[i]] === 1) {
unique_words.push(keys[i]);
}
}
return unique_words.sort();
}
console.log(get_unique_words(
['blah', 'blah', 'blah', 'goose', 'duck',
'mountain', 'rock', 'paper', 'rock', 'scissors']
));
Some issues and suggestions :
Don't use var twice for the same variable.
Browsers deal with it ok, but for clarity you should only be declaring your variables once.
Always localize your loop counters - forgetting a var before your i and j will cause them to become global variables.
This is relevant when you have a page with lots of code - all global variables will show up in the debugger's watch list at all times, making it harder to debug your code.)
Use the array literal notation [] instead of the function form Array.
The function form is longer and it's easier to forget the new. It's also easier to read (IMO).
Use more whitespace (it won't bite), such as before and after an equals sign:
var x = 1;
// vs.
var x=1;
It makes the code easier to read and most people don't overdo it.
Indent your code when it's inside a block (e.g. function, if, else, while, for, etc.).
This makes it easier to read the control flow of the code and will help prevent bugs.
Use three equals signs (===) unless you are using loose equality on purpose.
This will help someone looking at your code later (probably yourself) understand better what the test is supposed to be testing.

Javascript 'First or Default' function for 'associative arrays'/objects

Is there a better way to do this?
I'm storing values in what some would erroneously call an associated array:
The tokens object stores.... tokens and a count of documents using that token on a per-db level.
var tokens = {'db1' : { '654321': { 'docCount': 1 },
'321456': { 'docCount': 2 } },
'db2' : { '999999': { 'docCount': 1 } } };
I can add/remove dbs and tokens and update the docCounts appropriately.
We can assume, due to code omitted for brevity, that if a db exists, a token also exists with a docCount of at least 1.
If a db exists and I need to retrieve ANY of its tokens, what is the best method?
If the dbs held arrays, it would be as easy as tokens['db1'][0]... but I'm not using arrays.
I have something like the following, "inspired" by LINQ (please don't blame LINQ):
// NOTE: default not implemented here
var firstOrDefault = function(obj) {
var thing;
for (var i in obj) {
thing = i;
break;
}
return thing;
};
which would be called as so (simplified for example):
var anyToken;
if (tokens['db1') { anyToken = firstOrDefault(tokens['db1']); }
Generally returning per the above example '654321' (as this is an object, not an array, order is not guaranteed, but either value is acceptable in my code).
Is this a reasonable method to get any value?
Is there a better method?
Should I just suck it up, shove everything into an array, and wrap the storage features that way?
UPDATE: I've removed the default reference, as an unfound item will a perfectly acceptable undefined response:
// NOTE: obj.hasOwnProperty not implemented for brevity
var firstOrAny = function(obj) {
var thing;
for (var i in obj) {
thing = i;
break;
}
return thing;
};
which would be called as so (simplified for example):
var anyToken;
if (tokens['db1') { anyToken = firstOrAny(tokens['db1']); }

Slightly shorter solution:
var firstOrDefault = function(obj, d) {
for (var i in obj)
{
if (obj.hasOwnProperty(i))
{
return obj[i];
}
}
return d;
};
But yes, it is the fastest way to get any (usually first inserted) key from an object.
I also added a hasOwnProperty check to prevent cases where the values are retrieved from the prototype chain.

How do I change the Array in place when prototyping

I'm writing a custom sort function that I'm prototyping into Array. (PLEASE don't post answers explaining to me how I shouldn't bother prototyping into Array for whatever reason you feel prototyping into Array isn't a good idea).
so, my method looks like this:
//method
Array.prototype.mySort = function(memberName, ascOrDesc){
var labelRow = this.shift();
var ret = this.sort((function (a,b){
if(ascOrDesc > 0)
return (a[memberName] > b[memberName])?1:-1;
return (a[memberName] < b[memberName])?1:-1;
}));
ret.unshift(labelRow)
return ret;
}
Notice how this.shift() will affect the Array IN PLACE.
However, I'm not clear on how this is accomplished. If I wanted to write my own myShift method, at some point I'd need to say something to the effect of
this = this.myShift();
which is obviously illegal.
So, I'm trying to understand how shift() gets access to the array's members and is able to remove the first one in-place. And if I'm allowed to do something analogous, or if this is somehow baked in and not available to me to use.

You can access the array using this inside the method.
You can for example implement the shift method as:
Array.prototype.myShift = function() {
if (this.length == 0) return null;
var result = this[0];
for (var i = 1; i < this.length; i++) {
this[i-1] = this[i];
}
this.length--;
return result;
};

The problem is that you can't assign to this. This means you can't do things like this:
Array.prototype.myShift = function() {
this = this.slice(1);
};
This is because Array.prototype.slice returns a new array and does not modify the old array. Other methods, however, such as Array.prototype.splice, do modify the old array. So you can do something like this:
Array.prototype.myShift = function() {
return this.splice(0, 1)[0];
};
This will have exactly the same behaviour as the standard Array.prototype.shift method. It modifies the current array, so you can do this:
var labelRow = this.myShift();

Passing dynamic key-value pairs to function

I am probably overlooking something or just being a noob but, I am having trouble being able to pass key-value pairs to a javascript function.
I am writing a filter module utilizing a Backbone.View and Backbone.Paginator.clientPager collection. I added a function to the clientPager called whereExpanded() which searches the entire collection without modifying/rendering anything.
Backbone.Paginator.clientPager.prototype.whereExpanded = function(attrs) {
return _.filter(this.origModels, function(model) {
var key;
for (key in attrs) {
if (attrs[key] !== model.get(key)) {
return false;
}
});
};
As you can see, it takes the attrs variable and loops over it. I want to be able to pass in key value pairs to this but, the key and value need to be dynamic.
collection.whereExpanded(filterByField, filterByValue)
filterByField is the attribute of the Backbone.Model I wish to filter by and filterByValue is the value of the attribute I want to filter. I have tried utilizing eval() but I cannot seem to get that to work either.
Any help woudl be greatly appreciated!

You don't need eval for this, you can build an object in better ways:
var attrs = { };
attrs[filterByField] = filterByValue;
And with a small bit of effort, you can let your function be called in various different ways:
whereExpanded({ k1: v1, k2: v2 });
whereExpanded('k1', v1);
whereExpanded('k1', v1, 'k2', v2);
You just need to parse arguments yourself with something like this:
argv = [].slice.call(arguments);
attrs = {};
if(argv.length == 1 && _(argv[0]).isObject()) {
attrs = argv[0];
}
else if(argv.length % 2 == 0) {
for(var i = 0; i < argv.length; i += 2) {
attrs[argv[i]] = argv[i + 1];
}
}
else {
throw 'Bad argument list';
}
That will leave you with the key/value pairs in attrs that your _.filter is expecting.
Argument parsing demo: http://jsfiddle.net/ambiguous/e5kkc/

It looks like eval() did work in the end. I was being a noob.
eval("collection.whereExpanded({" + filterByField + ": " + filterByValue + "})")