Develop Reference

Retrieving single parts of a javasript/jquery object

Hi suppose I have a jQuery selector such as this:
var a = $(this);
var b = a.nextUntil("button").text();
This will retrieve all the DOM elements till the next button. I want to access all these DOM elements individually as separate objects. Is there way to do that?

If you want to execute a function for each of the elements, you can use .each
If you want all the objects to be in an array, you can do something like this:
var arr = a.nextUntil("button")
and then index it as an array.
console.log($(a[0]).text())

Getting array out of data attribute without jQuery

I want to work with an array to pass through using data-attribute.
In my HTML-tag I've this attribute:
data-toshow='["tblp"]'
I can access and use it with jQuery when using
$().data('toshow')
But when using dataset.toshow I don't get the same result. I actually don't get an array.
Can someone explain this to me? And give me the answer how to do the same without the use of jQuery?

jQuery's .data() method automatically tries to convert the string in your custom data attribute to whatever type it appears to be (in this case an array). JavaScript just treats it as a string, so you need to parse the string to get the same array output you get with jQuery. For example:
// jQuery approach
const jqtest = $('div').data('toshow');
console.log(jqtest);
// Plain JavaScript approach
const jstest = JSON.parse(document.querySelector('div').dataset.toshow);
console.log(jstest);
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div data-toshow='["tblp"]'></div>

//Use dataset to get a string of all data-* props
const stringVal = document.querySelector('#divA').dataset['toshow'];
//Parse the value of "data-toshow" to get your array
const array = JSON.parse(stringVal);
console.log(array);
<div id="divA" data-toshow='["tblp"]'></div>

Assuming you have HTML similar to:
<div id="theThing" data-toshow='["tblp"]'></div>
or
<div id="theThing" data-toshow='["tblp","arrItem2","arrItem3"]'></div>
//jQuery
var container_jq = $("#theThing");
var container_jq_dataArr = decodeURIComponent(container_jq.data('toshow')).split(",");
//vanilla
var container_vanilla = document.getElementById("theThing");
var container_vanilla_dataArr = JSON.parse(decodeURIComponent(container_vanilla.dataset.toshow));
console.info({jQuery: container_jq_dataArr,vanilla: container_vanilla_dataArr});
jsfiddle in action

Every HTMLElement has dataset property, this property could be null if there is no data attribute in the element, but if there is any data attribute, the dataset property is an array containing all the data values declared on the element.
Given an html like <div data-name='Usher' data-max-number='5'> There are two ways you can get this data attribute using javascript,
One way is to call the element.getAttribute('data-name') or element.getAttribute('data-max-number') of that element.
The second way is through the dataset property of the element. which you would use element.dataset.name to obtain the name attribute or element.dataset.maxNumber
NOTE: How max-number becomes maxNumber. This is how you access hyphen seperated data-set attribute, using camelCase

How to get the last element of a json file with jquery

$.getJSON('./file-read?filename='+filename+'&parameter='+parameter, function(data) {
var firstElement = data[0][0];
var lastElement = ?
});
I try to find out the last Element in my JSON file.
My JSON File looks like this:
[[1392418800000,6.9],[1392419400000,7],[1392420000000,7.1],[1392420600000,7.2],[1392421200000,7.2]]
can anybody help me to read extract the last date(1392421200000) ?

Just pick the (length - 1)th element with this:
var lastElement = data[data.length-1][0];
Another way is to use array methods, e.g. pop which will return the last element of the array:
var lastElement = data.pop()[0];
N.B.: The first approach is the fastest way of picking the last element, however the second approach will implicitly remove the last element from data array. So if you plan to use the initial array later in your code, be sure to use either the first method or alternative solution provided by #matewka.

VisioN's answer is nice and easy. Here's another approach:
var lastElement = data.slice(-1)[0];
// output: [1392421200000,7.2]
Negative number in the slice method makes the slice count from the end of the array. I find this method more compact and simpler but the disadvantage is that it returns a smaller, 1-element array instead of the element you wanted to fetch. If you want to fetch only the timestamp you'd have to add another [0] to the end of the expression, like this:
var lastElement = data.slice(-1)[0][0];
// output: 1392421200000

You can use :
var data = " any json data";
var lastelement = data[ Object.keys(obj).sort().pop() ];
Object.keys (ES5, shimmable) returns an array of the object's keys. We then sort them and grab the last one.

jQuery parsing html into JSON

I am currently using the following code:
jQuery('#book-a-service').click(function(){
var selectedServices = jQuery('.selected').parent().parent().html();
console.log(selectedServices);
});
and that returns:
<td rowspan="3">Brakes</td>
<td class="service-title">BRAKES SET</td>
<td class="service-description"><p>Setting of front and rear brakes for proper functioning (excluding bleeding)</p></td>
<td class="service-price">R <span id="price-brakes-set">R75</span><div id="select-brakes-set" class="select-service selected"></div>
</td>
which is what i want, except i need an array of all the elements with '.selected' class in JSON.. i just want to know how i could almost parse it in a way that i only get the contents of the td tags and as for the "service-price" only the numeric value and then how would i insert those values into a json object?
Any Help Greatly Appreciated..

jQuery is not my most formidable frameworks, but this seems to do the trick.
jQuery('#book-a-service').click(function(){
var selected = jQuery('.selected');
selected.each( function() {
var children = jQuery(this).parent().parent().find('td');
var json = {};
console.log(children);
json.type = jQuery(children[0]).text();
json.title = jQuery(children[1]).text();
json.description = jQuery(children[2]).find('p').text();
json.price = jQuery(children[3]).find('span#price-brakes-set').text();
console.log(json);
console.log(JSON.stringify(json));
});
});
in action: http://jsfiddle.net/3n1gm4/DmYbb/

When various elements share the same class and you select them with $(".class"), you can iterate through all of them using:
$(".selected").each(function() {
var element = $(this); // This is the object with class "selected" being used in this iteration
var absoluteParent = $(this).parent().parent();
// Do whatever you want...
var title_element = $(".service-title", absoluteParent); // Get service-title class elements in the context provided by "absoluteParent", I mean, "inside" of absoluteParent
var title = title_element.html();
});
In the specific case of prices, I don't know exactly what is the price (probably R75?). Anyway, it should be inside a div and then select that div to obtain the price. If it is R75, then note that the "id" property should be unique for every DOM object in your HTML.
Also note that, when getting HTML, you're only getting a string, not the actual element, so it will probably not be useful for getting new values in an easy way (you won't be able to navigate through DOM elements with an ordinary string, even if it represents HTML from an actual object). Always get jQuery objects and work with them, unless you actually need the HTML.
For generating a JSON string, just create a global array and add the objects/values you need there. Then you can obtain a JSON string using var jsonText = JSON.stringify(your_array);
Consider not doing this in Javascript, as it's not useful in the majority of cases. Just send the values through POST value to a script (PHP, for example) and in the PHP you will get the actual value. The other way (PHP to Javascript) will be useful to return JSON (using json_encode($a_php_array)) and then, in Javascript, transform to a JS array using var my_array = JSON.parse(the_string_returned_by_php);.

Setting the last element of an array to a separate String and then removing said element

I have an array that could have between 1 and 11 elements. I want to remove the last element and make it a new string, then set the rest of the arraylist to a collective string. The following code isn't working...Do I need to include an if else incase the arraylist has only one element? (I know I do, I'm wondering if that would cause the script not to be executed at all)
var finaling = checked[checked.length].toString();
checked.splice(checked[checked.length]);
checked.toString();

Here is how I would do it...
I want to remove the last element...
checked.pop();
...and make it a new string...
checked.push('new string');
// or skip the above `pop()`
checked[checked.length - 1] = 'new string';
...then set the rest of the arraylist to a collective string.
checked = checked + '';
The default toString() of an array will join the elements with a ','. If you want to use a different joining character, use join().

I'm not sure what you're trying to do but this should do it:
var lastElementInArray = checked.splice(checked.length-1)[0].toString();
var stringOfChecked = checked.toString();
Or if you want to remove the last element of an array and return a string representing the new array:
checked.splice(checked.length-1, 1);
var finaling = checked.toString();
Something to note: array.splice() returns an array of elements; if you only have one element in it and you want that actual element, you'll want to use array.splice(...)[0].