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How to find longest length array within an array of an object?

I am trying to come up with a single function that returns the object with the longest length array within an array.
Here is the question:
Write a function that lists all the Orcs that have the most the weapons.
Example:
var orcs = [{
name: 'Orgoth',
strength: 9001,
weapons: ['Bone ax', 'Mace of Strength']
}, {
name: 'Blaroguhh',
strength: 500,
weapons: ['Cheeseburger', 'Spear of the Hut']
}, {
name: 'Mark',
strength: 543,
weapons: ['Ax of Defense', 'Dagger', 'Sword']
}]
getMostWeapons(orcs);
// => {name: 'Mark', strength: 543, weapons: ['Ax of Defense', 'Dagger', 'Sword' ]}
And this is what I have so far:
function getMostWeapons(orcs) {
var length = 0;
return orcs.filter(function (obj) {
return obj.filter(function (val) {
if (val.length > length) {
return (length = val.length);
}
});
});
}

.filter is used to return all the array elements that match a criteria. Since you don't know the maximum length until you've gone through all the orcs, you can't use it in one pass to find the orc to return.
Just use an ordinary loop that compares the length of weapons to the longest seen so far. If it's longer, replace the longest with this one.
function getMostWeapons(orcs) {
var longest = 0;
var longestOrcs = [];
orcs.forEach(function(orc) {
if (orc.weapons.length > longest) {
longestOrcs = [orc];
longest = orc.weapons.length;
} else if (orc.weapons.length == longest) {
longestOrcs.push(orc);
}
});
return longestOrcs;
}

.filter() isn't really what you want here because you wouldn't know what you were filtering for without first making a pass to see what the max length was. .reduce() could be used (for side effects), but you aren't really accumulating a single value here like .reduce() is built for. So, it makes sense to just use .forEach() with a couple parent-scoped variables to keep track of our state.
To return all objects that have the max length, you can do this (in a snippet you can run to see the results). This returns an array of all objects that have the maximum length.
var orcs = [{
name: 'Orgoth',
strength: 9001,
weapons: ['Bone ax', 'Mace of Strength']
}, {
name: 'Blaroguhh',
strength: 500,
weapons: ['Cheeseburger', 'Spear of the Hut']
}, {
name: 'Mark',
strength: 543,
weapons: ['Ax of Defense', 'Dagger', 'Sword']
}];
function getMostWeapons(o) {
var max = 0, maxObj = [];
o.forEach(function(item) {
if (item.weapons.length > max) {
max = item.weapons.length;
maxObj = [item];
} else if (item.weapons.length === max) {
maxObj.push(item);
}
});
return maxObj;
}
var max = getMostWeapons(orcs);
log(max);
function log(x) {
document.write(JSON.stringify(x));
}

You can use filter although it's nearly unreadable and cannot be called "good coding" with a clear conscious but when others can use forEach with a function instead of a simple loop without any good reason ... ;-)
JSON.stringify(
orcs.sort(function(a,b){
return b.weapons.length - a.weapons.length;
}).filter(function(value,index,array){
return value.weapons.length == array[0].weapons.length;
})
)

I'd separate into two functions, one to find the max, and one to find all orc with that max:
function getMostWeapons(allOrcs) {
return allOrcs.reduce((max, currentOrc) =>
Math.max(max, currentOrc.weapons.length), 0);
}
function getOrcsWithMostWeapons(allOrcs) {
let maxWeapons = getMostWeapons(allOrcs);
return allOrcs.filter(orc => orc.weapons.length === maxWeapons);
}
Note that this will return an array even if there's only one orc. I find it best to always return the same type.

Try like this
var length=Math.max.apply(Math,orcs.map(function(o){return o.weapons.length;}));
var obj=orcs.find(function(x){ return x.weapons.length == length;}); // single object
var objList=orcs.filter(function(x){ return x.weapons.length == length;}); // multple
console.log(obj);
console.log(objList);
JSFIDDLE

Late answer but good if anyone comes here looking for a similar answer, I took the current answer and converted it to use for in, a little more generic too
function getLargest(o) {
var max = 0, maxObj = [];
for ( var item in o)
{
if (o[item].length > max) {
max = o[item].length;
maxObj = [item];
} else if (o[item].length === max) {
maxObj.push(item);
}
};
return maxObj;
}

A simple loop with a length variable would probably be the best way
function getMostWeapons(orcs) {
var len = 0; //longest
for( x in orcs ){ //simple loop
len = len < orcs[x].weapons.length ? orcs[x].weapons.length : len;
}
}

Access by value on nested JSON arrays

I'm new to JavaScript and I'm really lost here. Here is some data produced by PHP json_encode() (and limited to most pertinent keys) :
[
{
"product_option_id":"229",
"product_option_value":
[
{
"product_option_value_id":"21",
"option_value_id":"51",
"price":"1,22 €",
"price_prefix":"+"
},
{
"product_option_value_id":"22",
"option_value_id":"52",
"price":false,
"price_prefix":"+"
},
{
"product_option_value_id":"23",
"option_value_id":"53",
"price":"2,42 €",
"price_prefix":"+"
}
],
"option_id":"14",
"type":"radio",
"value":""
},
{
"product_option_id":"228",
"product_option_value":
[
{
"product_option_value_id":"19",
"option_value_id":"49",
"price":"1,22 €",
"price_prefix":"+"
},
{
"product_option_value_id":"20",
"option_value_id":"50",
"price":"2,42 €",
"price_prefix":"+"
}
],
"option_id":"13",
"type":"select",
"value":""
}
]
I need to access price and price_prefix values (in JavaScript) knowing product_option_id and product_option_value_id.
How do I do that ? Should I go for a loop ?
Update :
Thanks for replies. Unless I missed something, it appears that in my case arrays (as ugly as they may be…) are much more efficient than all the proposed solutions (I'll try another approach, formatting a JSON object corresponding to my needs with PHP rather than using the "default" one, but it's off topic here). Though I'm not fond of adding libraries and it's a bit slower than most other solutions, I'll accept Matt's solution because it really seems to make life easier as far as JSON access is concerned. But it should be noted that Yeldard and Barmar's (almost cloned) solutions are faster than other propositions.

lodash would make this easier and neater. It provides _.find or _.filter depending on if your id's are unique or not.
var record = _.find( data_structure, {
"product_option_id": "229"
})
if ( !record ) throw new Error("Record not found");
var value = _.find( record.product_option_value, {
"product_option_value_id":"22"
})
if ( !value ) throw new Error("Value not found");
console.log( "price[%s] prefix[%s]", value.price, value.price_prefix )
Demo
For more complex data selection, you might want to look at sift.js. It's based on mongodb's query system.
var records = sift({
"product_option_id": "229",
"product_option_value": {
$elemMatch: {
"product_option_value_id": "22"
}
}
},
data_structure
)

you can do like this
for(var i in jsonData) {
var item = jsonData[i];
if(item.product_option_id == 229) {
for(var j in item.product_option_value){
var item1 = item.product_option_value[j];
if(item1.product_option_value_id == 21) {
//your item here
break;
}
}
break;
}
}

This should do it:
var productOptionId = 229;
var productOptionValue = 22;
var matchingOuter = yourData.filter(function(i){
return i.product_option_id === productOptionId;
})[0];
if (matchingOuter) {
var matchingInner = matchingOuter.product_option_value.filter(function(i){
return i.product_option_value === productOptionValue;
})[0];
}
If a matching item exists it will be assigned to matchingInner

Following would do:
function getProductValues(products, product_option_id, product_option_value_id) {
if (!product_option_id || !product_option_value_id) {
return;
}
return products.filter(function(product) {
return +product.product_option_id === product_option_id;
}).map(function (product) {
var option_values = product.product_option_value;
return option_values.filter(function (option) {
return +option.option_value_id === product_option_value_id;
})[0] || [];
})[0] || [];
}
Usage:
getProductValues(data, 229, 51)
Result:
{product_option_value_id: "21", option_value_id: "51", price: "1,22 €", price_prefix: "+"}

Use filter on the main array to grab the right object, filter again on the option_value_id, then map on the returned array to get a single price/prefix object. map and filter both return arrays which is why you see the code picking up the first element ([0]) in a couple of places.
function getData(data, options) {
return data.filter(function (product) {
return product.product_option_id === options.id;
})[0].product_option_value.filter(function (details) {
return details.product_option_value_id === options.optionId;
}).map(function(el) {
return { price: el.price, prefix: el.price_prefix }
})[0];
}
getData(data, { id: '229', optionId: '23' }); // { price: "2,42 €", prefix: "+" }
DEMO

Use nested loops to search through the main array and the sub-arrays, looking for the matching element.
function find_product(product_option_id, product_option_value_id) {
for (var i = 0; i < products.length; i++) {
var product = products[i];
if (product.product_option_id == product_option_id) {
for (var j = 0; j < product.product_option_value.length; j++) {
var value = product.product_option_value[j];
if (value.product_option_value_id == product_option_value_id) {
return { price: value.price, price_prefix: value.price_prefix }
}
}
}
}
}

Yes, you need to enumerate through the array and find your items:
Here is the working code which outputs price_prefix and price of product with product_option_id = 228 and product_option_value_id = 19. You can replace these values with your own.
for (var i = 0; i < obj.length; i++) // Enumerate through array
{
var item = obj[i];
if (item.product_option_id === "228") // Filtering items by product_option_id
{
// When necessary product_option_id found
for (var j = 0; j < item.product_option_value.length; j++) // Enumerate through its products
{
var productItem = item.product_option_value[j];
if (productItem.product_option_value_id === "19") // Filtering by product_option_value_id
{
// here it is. productItem is found! do whatever you want with it
alert(productItem.price_prefix + " " + productItem.price);
}
}
}
}
Working JSFiddle demo.

Check if an object with index is in array

$.each(constructions, function(i,v) {
if ($.inArray(v.name, map[ii].buildings) == -1) {//stuff}
};
Where constructions is an array of objects, each with a unique name. map[ii].buildings is an array containing some of these objects. I want to iterate each object in constructions, checking if its name parameter appears in the objects of map[ii].buildings.
The above code works if the each element in the map[ii].buildings array is just the text string of the object name, but not if the element is the entire object.. close, but no dice >.<

Try using $.grep() instead of $.inArray(); you can specify a function to do the filtering for you.
Instead of checking for -1, you check whether the array that $.grep() returns has length == 0
Simple example: (would be easier if you posted the code / example of what "constructions" objects look like)
var constructions = [{
Name: "Mess hall",
SqFt: 5000
}, {
Name: "Infirmary",
SqFt: 2000
}, {
Name: "Bungalow",
SqFt: 2000
}, {
Name: "HQ",
SqFt: 2000
}];
var buildings = [{
Name: "Infirmary",
SqFt: 2000
}, {
Name: "HQ",
SqFt: 2000
}];
// found buildings will be list of items in "constructions" that is not in "buildings"
var foundBuildings = $.grep(constructions, function (constructionsItem) {
return $.grep(buildings, function (buildingsItem) {
return buildingsItem.Name === constructionsItem.Name
}).length == 0; // == 0 means "not in", and > 0 means "in"
});
// this just renders the results all pretty for ya
$.each(foundBuildings, function (idx, item) {
$("#output").append("<div>" + item.Name + "</div>");
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div id='output'></div>
Example jsFiddle: http://jsfiddle.net/eLeuy9eg/3/

The non-jQuery way of doing this would be to use filter. Something like this:
// pass in an array and the key for which you want values
// it returns an array of those values
function getValues(arr, key) {
return arr.map(function (el) { return el[key]; });
}
function notFoundIn(arr, arr2) {
// grab the names of the buildings
var buildings = getValues(arr2, 'name');
// grab the names from the construction objects and filter
// those that are not in the building array
return getValues(arr, 'name').filter(function (el) {
return buildings.indexOf(el) === -1;
});
}
notFoundIn(constructions, buildings); // eg [ "one", "three" ]
DEMO
You could even add a new method to the array prototype. With this one you can use either simple arrays, or arrays of objects if you pass in a key. Note in this example I've replaced map and filter with loops that perform the same functions, but faster (see comments):
function getValues(arr, key) {
var out = [];
for (var i = 0, l = arr.length; i < l; i++) {
out.push(arr[i][key]);
}
return out;
}
if (!Array.prototype.notFoundIn) {
Array.prototype.notFoundIn = function (inThisArray, key) {
var thisArr = key ? getValues(this, key) : this;
var arrIn = key ? getValues(inThisArray, key) : inThisArray;
var out = [];
for (var i = 0, l = thisArr.length; i < l; i++) {
if (arrIn.indexOf(thisArr[i]) === -1) {
out.push(thisArr[i]);
}
}
return out;
}
}
constructions.notFoundIn(buildings, 'name');
[1, 2, 3].notFoundIn([2]); // [1, 3]
DEMO

Remove duplicate objects from an array using javascript

I am trying to figure out an efficient way to remove objects that are duplicates from an array and looking for the most efficient answer. I looked around the internet everything seems to be using primitive data... or not scalable for large arrays. This is my current implementation which is can be improved and want to try to avoid labels.
Test.prototype.unique = function (arr, artist, title, cb) {
console.log(arr.length);
var n, y, x, i, r;
r = [];
o: for (i = 0, n = arr.length; i < n; i++) {
for (x = 0, y = r.length; x < y; x++) {
if (r[x].artist == arr[i].artist && r[x].title == arr[i].title) {
continue o;
}
}
r.push(arr[i]);
}
cb(r);
};
and the array looks something like this:
[{title: sky, artist: jon}, {title: rain, artist: Paul}, ....]
Order does not matter, but if sorting makes it more efficient then I am up for the challenge...
and for people who do not know o is a label and it is just saying jump back to the loop instead of pushing to the new array.
Pure javascript please no libs.
ANSWERS SO FAR:
The Performance Test for the answers below:
http://jsperf.com/remove-duplicates-for-loops

I see, the problem there is that the complexity is squared. There is one trick to do it, it's simply by using "Associative arrays".
You can get the array, loop over it, and add the value of the array as a key to the associative array. Since it doesn't allow duplicated keys, you will automatically get rid of the duplicates.
Since you are looking for title and artist when comparing, you can actually try to use something like:
var arrResult = {};
for (i = 0, n = arr.length; i < n; i++) {
var item = arr[i];
arrResult[ item.title + " - " + item.artist ] = item;
}
Then you just loop the arrResult again, and recreate the array.
var i = 0;
var nonDuplicatedArray = [];
for(var item in arrResult) {
nonDuplicatedArray[i++] = arrResult[item];
}
Updated to include Paul's comment. Thanks!

Here is a solution that works for me.
Helper functions:
// sorts an array of objects according to one field
// call like this: sortObjArray(myArray, "name" );
// it will modify the input array
sortObjArray = function(arr, field) {
arr.sort(
function compare(a,b) {
if (a[field] < b[field])
return -1;
if (a[field] > b[field])
return 1;
return 0;
}
);
}
// call like this: uniqueDishes = removeDuplicatesFromObjArray(dishes, "dishName");
// it will NOT modify the input array
// input array MUST be sorted by the same field (asc or desc doesn't matter)
removeDuplicatesFromObjArray = function(arr, field) {
var u = [];
arr.reduce(function (a, b) {
if (a[field] !== b[field]) u.push(b);
return b;
}, []);
return u;
}
and then simply call:
sortObjArray(dishes, "name");
dishes = removeDuplicatesFromObjArray(dishes, "name");

Basic sort-then-unique implementation, fiddle HERE:
function unique(arr) {
var comparer = function compareObject(a, b) {
if (a.title == b.title) {
if (a.artist < b.artist) {
return -1;
} else if (a.artist > b.artist) {
return 1;
} else {
return 0;
}
} else {
if (a.title < b.title) {
return -1;
} else {
return 1;
}
}
}
arr.sort(comparer);
console.log("Sorted: " + JSON.stringify(arr));
for (var i = 0; i < arr.length - 1; ++i) {
if (comparer(arr[i], arr[i+1]) === 0) {
arr.splice(i, 1);
console.log("Splicing: " + JSON.stringify(arr));
}
}
return arr;
}
It may or may not be the most efficient, and should be entirely scalable. I've added some console.logs so you can see it as it works.
EDIT
In the interest of saving on the space the function used, I did that for loop at the end, but it seems likely that didn't properly find only unique results (depsite it passing my simple jsfiddle test). Please try replacing my for loop with the following:
var checker;
var uniqueResults = [];
for (var i = 0; i < arr.length; ++i) {
if (!checker || comparer(checker, arr[i]) != 0) {
checker = arr[i];
uniqueResults.push(checker);
}
}
return uniqueResults;

I use this function. its not doing any sorting, but produces result. Cant say about performance as never measure it.
var unique = function(a){
var seen = [], result = [];
for(var len = a.length, i = len-1; i >= 0; i--){
if(!seen[a[i]]){
seen[a[i]] = true;
result.push(a[i]);
}
}
return result;
}
var ar = [1,2,3,1,1,1,1,1,"", "","","", "a", "b"];
console.log(unique(ar));// this will produce [1,2,3,"", "a", "b"] all unique elements.

Below is Henrique Feijo's answer with ample explanation and an example that you can cut and paste:
Goal: Convert an array of objects that contains duplicate objects (like this one)...
[
{
"id": 10620,
"name": "Things to Print"
},
{
"id": 10620,
"name": "Things to Print"
},
{
"id": 4334,
"name": "Interesting"
}
]
... Into an array of objects without duplicate objects (like this one):
[
{
"id": 10620,
"name": "Things to Print"
},
{
"id": 4334,
"name": "Interesting"
}
]
Explanation provided in the comments:
var allContent = [{
"id": 10620,
"name": "Things to Print"
}, {
"id": 10620,
"name": "Things to Print"
}, {
"id": 4334,
"name": "Interesting"
}]
//Put Objects Into As Associative Array. Each key consists of a composite value generated by each set of values from the objects in allContent.
var noDupeObj = {} //Create an associative array. It will not accept duplicate keys.
for (i = 0, n = allContent.length; i < n; i++) {
var item = allContent[i]; //Store each object as a variable. This helps with clarity in the next line.
noDupeObj[item.id + "|" + item.name] = item; //This is the critical step.
//Here, you create an object within the associative array that has a key composed of the two values from the original object.
// Use a delimiter to not have foo+bar handled like fo+obar
//Since the associative array will not allow duplicate keys, and the keys are determined by the content, then all duplicate content are removed.
//The value assigned to each key is the original object which is along for the ride and used to reconstruct the list in the next step.
}
//Recontructs the list with only the unique objects left in the doDupeObj associative array
var i = 0;
var nonDuplicatedArray = [];
for (var item in noDupeObj) {
nonDuplicatedArray[i++] = noDupeObj[item]; //Populate the array with the values from the noDupeObj.
}
console.log(nonDuplicatedArray)

For those who love ES6 and short stuff, here it's one solution:
const arr = [
{ title: "sky", artist: "Jon" },
{ title: "rain", artist: "Paul" },
{ title: "sky", artist: "Jon" }
];
Array.from(arr.reduce((a, o) => a.set(o.title, o), new Map()).values());
const arr = [
{ title: "sky", artist: "Jon" },
{ title: "rain", artist: "Paul" },
{ title: "sky", artist: "Jon" },
{ title: "rain", artist: "Jon" },
{ title: "cry", artist: "Jon" }
];
const unique = Array.from(arr.reduce((a, o) => a.set(o.title, o), new Map()).values());
console.log(`New array length: ${unique.length}`)
console.log(unique)
The above example only works for a unique title or id. Basically, it creates a new map for songs with duplicate titles.

Below code compares object with JSON as String format and removes duplicates and works fine with simple arrays.
Array.prototype.unique=function(a){
return function(){
return this.filter(a)
}
}(
function(a,b,c){
var tmp=[];
c.forEach(function(el){
tmp.push(JSON.stringify(el))
});
return tmp.indexOf(JSON.stringify(a),b+1)<0
})

If you are using underscore js, it is easy to remove duplicate object.
http://underscorejs.org/#uniq

function remove_duplicates(objectsArray) {
var arr = [], collection = [];
$.each(objectsArray, function (index, value) {
if ($.inArray(value.id, arr) == -1) {
arr.push(value.id);
collection.push(value);
}
});
return collection;
}

JS .indexOf('string') returns -1

I have an Array[] this.unusedInstruments:
[
{ label: 'one'},
{ label: 'two'},
{ label: 'three'}
]
and a function: (params getting passed in are verified as being 'one', 'two', or 'three'
removeInstrument: function(removedIntrument) {
var index = this.unusedInstruments.indexOf(removedIntrument);
delete this.unusedInstruments[index];
},
but I am not getting what I expected. I logged the index, and it is always returning -1 despite the parameter. I am assuming that it is saying that the index doesn't exist, but I guess that means I don't know how to query the parent Array for the indexed Object.

As soon as it's an array - you cannot just delete its elements, otherwise you'll get a holes with undefined value. So you need a bit more intelligent way of doing that:
removeInstrument: function(removedInstrument) {
var len = this.unusedInstruments.length,
i;
var remove = function(arr, from) {
// Based on John Resig's article (MIT Licensed)
// http://ejohn.org/blog/javascript-array-remove/
var rest = arr.slice(from + 1);
arr.length = from;
return arr.push.apply(arr, rest);
};
for (i = 0; i < len ; ++i) {
if (this.unusedInstruments[i].label == removedInstrument) {
remove(this.unusedInstruments, i);
break;
}
}
}
remove() function implementation idea is borrowed at https://stackoverflow.com/a/9815010/251311

.indexOf() will only work if the string is an element of the array you're searching. But in your data, the string is the value of the label property of the element, it's not the element itself. You need to write a loop that drills into the objects and compares with the property.
removeInstrument: function(removedInstrument) {
for (i = 0; i < this.unusedInstruments.length; i++) {
if (this.unusedInstruments[i].label == removedInstrument) {
delete this.unusedInstruments[i];
break;
}
}
}