Develop Reference

Better way to get an unique object out of an array

I have an array with objects. Each object got an unique id. What is the best way to get a specific object from the array?
Currently I use something like this
this.getObjectById = function(objectId){
return $.grep(this.objects, function(e){ return e.id === objectId; })[0];
}
but the fact that
$.grep();
returns an array of results I don't know if I should go for this. Because currently I take the first element of this array and it's fine because I just got one element in it.
But is there a more clean way?
Is
Array.prototype.find()
a better one?

Find is faster since it returns the first match, while jquery grep loops trough entire array. If you need full browser support just create you own function:
this.getObjectById = function(objectId){
for(var i = 0; i<this.objects.length; i++){
if(objectId == this.objects[i].id) return this.objects[i];
}
return null;
}

Use underscore.js _.find() method to iterate your collection.

How to compare two objects

I have a scenario, where I have two different Objects.
Scenario to achieve:
From two objects I need to match the values which has "A1","B2", etc...
Since both the objects values are not in proper order, the loop is breaking and missing some values.
In my demo the object1 has same repeated value i.e. "C3", It should be displayed only once.
Final output required is I need to detect only the matched values from two objects and display its corresponding "a" and "b values."
I have tried almost 90%, but somewhere some minor error is breaking my loop, Please help me out.
Sample code:
for(var i=0;i<obj1.results[0].loc.length;i++){
var findA = obj1.results[0].loc[i].anc[0].title;
for(var j=0;j< obj2.ILoc.length;j++){
var findB = obj2.ILoc[j].ais;
if(findA == findB) {
var a = obj1.results[0].loc[i].a;
var b = obj1.results[0].loc[i].b;
console.log(a);
console.log(b);
}
}
}
This is what I have tried:
Demo Link

I would recommend using for...in loop, since you're using objects instead of arrays.
for (variable in object) {...
}
If length property of both objects is equal, then this kind of loop alone will help you to compare objects with ease.

I would recommend using the diff module. You can use it in node.js and the browser.

Javascript removing and rearranging array elements

I have this collection of images resources where that is stored in array, the user will select an image and then the selected image will be removed from the list(also from the array) and after that The array would be rearrange. How could I perform such task? (as much as possible I do not want to use an open source library)

Sounds like you need to look up splice() method. It allows you to add and remove one to many items within an array at any index.
here's reference for it.
https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Array/splice

your question lacks a code example but you can use Array.splice(index,number) whereas index is zero based and number is how many items to remove.
images.splice(selectedIndex,1);

Simply, you can create a temporary array where you store the initial array elements you need and reassign the value of your initial array to the temporary array.
function clean_array(my_array){
var no_need_value = 'value you want to remove'
var tmpArray = new Array()
for (var i = 0; i < my_array.length; i++)
if (my_array[i] != no_need_value)
tmpArray.push(my_array[i])
my_array = tmpeArray
}

best way to append an item to a list within a JSON object?

I'm working on JavaScript and I have this JSON object:
var obj ={"name" : "objName",
"dynamicList" :[]};
and then I add some items to my list like this:
obj.dynamicList["someStringID"] = {"watever"};
It's important that I use a string as indexer for each item on my list (i didn't know this could be done until recently).
My only problem now is that whenever I ask for obj.dynamicList.lenght I get 0, unles I manually set the proper number... I was wondering if there's a better way to add items to my list?
Thanks!!

In Javascript, string index is not really an index. It's actually an attribute of the array object. You could set and get the value with the string index, but it's actually an empty array with some attributes. Not only .length, but also .sort(), .splice(), and other array function would not work. If there is a need to use array functions, I would use number as an index to make it a real item in the array.
If you have to use the string as an index, you couldn't rely on .length function. If there is no need to support IE prior to version 9, the Object.keys as suggested by #strimp099 should work. or you may have to create function to count the number of attributes for example:
function len(obj) {
var attrCount = 0;
for(var k in obj) {
attrCount++;
}
return attrCount;
}
and then call
len(obj.dynamicList);

Use the following the find the length of dynamicList object:
Object.keys(obj.dynamicList).length

To do this "the right way," you will have to make obj.dynamicList an object instead of an array; use {} instead of [] to set the initial value.

How to efficiently count the number of keys/properties of an object in JavaScript?
dynamiclist is an object, the length is not the length property you expect from an array.

json jquery filter javascript array

I have a json object array. I want to search the array and for each object, create a list of 'services' that is a comma-seperated list of all the keys which have a value of "yes".
The list of json objects with the services list is then displayed in html using jquery's each.
Its a large json file so I want to do it as efficiently as possible.
I already have the object's properties being accessed through jQuery's each (ie, obj.name)
-- so I think it should be possible to filter the services listed for each object using
jQuery's filter, and then display the key if the value is yes.
But it seems like a more efficient option would probably be to create a new javascript array, join the services with a value of yes and then add that variable to the html being
appended.
Im not sure which would be faster and so far havent been very successful at either... so any advice and examples would be very helpful.
Here's what the json array looks like:
[
{"name":"name1",
"service1":"y",
"service2":"y",
"service3":"n",
},
{"name":"name2",
"service1":"n",
"service2":"y",
"service3":"n",
},
];

If you just want to filter the array then use grep.
grep - Finds the elements of an array which satisfy a filter function. The original array is not affected.
http://api.jquery.com/jQuery.grep/

First off, delete trailing commas. Internet Explorer gets really, really confused by them. Anyway, I assume you don't want to "search" the array when you say "for each value"; you want to iterate through the array and parse it into a more usable list. The first method I'd suggest is just passing what you want as the array you desire, but if that's not an option, what you're looking for is some variant of this, which should be fairly efficient (jsFiddle example):
var json = [
{"name":"name1", "service1":"y", "service2":"y", "service3":"n"},
{"name":"name2", "service1":"n", "service2":"y", "service3":"n"}
];
var parsed = {};
for (var i = 0, iLen = json.length; i < iLen; i++) {
// Assuming all we need are the name and a list
var name;
var list = [];
for (var key in json[i]) {
var value = json[i][key];
// We need to hold on to the name or any services with value "y"
if (key === "name") {
name = value;
} else if (value === "y") {
list.push(key);
}
}
// Add them to the parsed array however you'd like
// I'm assuming you want to just list them in plain text
parsed[name] = list.join(", ");
}
// List them on the web page
for (var key in parsed) {
document.write(key + ": " + parsed[key] + "<br>");
}
That way you wind up with a display to the visitor of the services available and still keep an array around for further use if necessary.

jQuery.inArray() Search for a specified value within an array and return its index (or -1 if not found).
http://api.jquery.com/jQuery.inArray/
Or
http://api.jquery.com/jQuery.each/