Kind of a newbie to this but I have followed a totorial on a memory game as an attempt to understand the syntax of JS but am stuck on making the round result print in a instead of showing up as a alert
here is a codepen here.
how can I print round in a <span> <!-- result here--> </span> rather than like this alert("result")
How can I make it set to a span instead of being an alert?
Browsers parse HTML into a tree of objects called Document Object Model (DOM). Using JavaScript you can query the DOM to get individual nodes, and then change them.
To get your span, you would typically use document.getElementById or document.querySelector (there are other functions that can fetch collections of related nodes, like document.getElementsByClassName or document.querySelectorAll). The former identify nodes by the property named in the method name (ID, or class name, respectively); the latter ones use CSS selectors. (All of the getElement... functions can be replicated using the newer querySelector and querySelectorAll interface, though you have to know how to use CSS selectors. I almost never use getElement... functions any more.) There are also functions that use XPath, though this is a bit more advanced subject.
Once you have the node, you can change its content using e.g. .textContent or .innerHTML properties, the former being for plain text, the latter for HTML.
For example, if this is the only span on the page, this suffices:
document.querySelector('span').textContent = "Result";
<span></span>
If on the other hand you have more of them, you would need some way to target the correct one. I will also demonstrate how you can style it using HTML:
const node = document.querySelector('#result_goes_here');
node.innerHTML = "<strong>Result</strong> in bold!";
<span id="result_goes_here"></span>
If you are trying to add the result inside the HTML SPAN and not in the alert box. You can do it something like this:
document.getElementById("span_ID").innerHTML = the_variable_result_here;
Hope that helps!
Related
I am just beginning to learn client-side JavaScript and using an online tutorial, so please bear with me.
This question is based on my understanding of the following:
To access the properties of the document's body, the syntax is "document.body", which returns all the elements in the body.
Similarly when you access the head, you use "document.head". Makes sense and most importantly, it works.
However, when I attempt to access elements WITHIN the body or head following the same logic, I get a return value of "undefined". For example, document.body.h1, returns "undefined", in spite of there being an h1 element inside the body element.
Further, when I enter document.head.title -- "undefined".
Strangely, however, when I enter "document.title", it returns the string value associated with the title tag.
I thought in order to access the title, you would have to access it through the head, since it is an element nested inside the head. But ok, that's fine. Using the same logic, I should then be able to enter document.h1 and get its value. Nope, instead, I get undefined.
Would someone be kind enough to explain to me why this behavior is so inconsistent. Thanks in advance.
You've really asked two questions:
Why document.title rather than document.head.title?
and
Why doesn't document.body.h1 return an element if there's an h1 in the body?
document.title
document.title is historical. Various parts of the browser environment were developed somewhat ad hoc by multiple different people/organizations in the 1990s. :-) That said, it's the title of the document, so this isn't an unreasonable place to put it, even if you use the title tag in head.
document.body.h1
One answer is: Because no one decided to design it that way. There were some early things like document.all (a list of all elements in the document) and even tag-specific ones (I forget exactly what they were, but they weren't a million miles off your document.body.h1 — I think document.tags.h1 or something, where again it was a list.)
But another answer is: Because the DOM is a tree. body can have multiple h1 elements, both as direct children and as children of children (or deeper); collectively, descendants. Creating automatic lists with all of these proved not to be scalable to large documents.
Instead, you can query the DOM (either the entire document, or just the contents of a specific element) via a variety of methods:
getElementById - (Just on document) Get an element using its id attribute value.
querySelector - Find the first element matching a CSS selector (can use it on document or on an element). Returns null if there were no matches.
querySelectorAll - Get a list of all elements matching a CSS selector (can use it on document or on an element). You can rely on getting back a list; its length may be 0, of course.
getElementsByTagName - Get a list of all elements with a given tag name (such as "h1").
getElementsByClassName - (No support in IE8 and earlier) Get a list of all elements with a given class.
There are many more. See MDN's web documentation and/or the WHAT-WG DOM Standard for more.
Some of the automatic lists persist (they got so much use that they had to be maintained/kept), such as document.forms, document.links, the rows property on HTMLTableElement and HTMLTableSectionElement instances, the cells property on HTMLTableRowElement instances, and various others.
document.head.title is a thing... but not what you might think.
title is an attribute that is applicable to all html elements; that is, it is a global attribute. It's meaning is 'advisory information'; one use is to display a tooltip:
<span title="hover over me and you'll see this">information</span>
So, all elements have a title attribute - including head. The title element - which is completely different - should be a child of the head though. So you might be tempted to set its value via document.head.title = "my title" , but document.head.title is not the head's title element, it's a property of the head element.
What you're actually doing is setting the title property on the head element:
<head title="my title">.... </head>
... which isn't what you want at all.
The correct way to set the title is document.title, which is a shortcut way of doing
document.querySelector("title").innerText = "my title"
I dont know good method how to get DOM element from template by javascript.
Example template:
<script id = "template" type="text/template">
<div>text1</div>
<div>text2</div>
<div>text3</div>
</script>
For example i want get div with "text2"
There is ways which i know, all of them are bad:
Add "class" to all elements - it breaks semantics (class created for CSS). In big projects you must use very long names for classes, its very inconvenient.
Get element by his number (index) - when adding a new element, you must rewrite old numbers in your code.
I see a couple of options:
If you don't want to use class , you can use a data-* attribute.
Assuming you load the template once and then duplicate its contents as desired, you could put id values on the elements in the template, which you then remove when cloning them and adding them to the document (so you don't end up with the same id on more than one copy of the element, which would be invalid and probably counterproductive).
Maybe you can also create as many templates as you need.
One for each div.
If you need to get each div at a time you must set ids to them ... of course you can also browse the dom inside script element to find the one you're interested in ...
Home this helps
Regards
mimiz
Is there a way to select a child DOM object by treating it as data member of its parent DOM object? Imagine I have this code:
<div id=div1>
<div id=innerdiv1></div>
<div id=innerdiv2></div>
</div>
<div id=div2>
<div id=innerdiv1></div>
<div id=innerdiv2></div>
</div>
This example won't work in real life because both pairs of child divs have the same id's (innerdiv1, innerdiv2), but that's exactly what bothers me about the "id" thing.
Is there some way in javascript to access a child element as a data member, something like document.getElementById('div1.innerdiv1'), which would return a different object from document.getElementById('div2.innerdiv1').
I can't stand that each id has to be unique throughout the document. It becomes a major issue when you have a lot of code and you accidentally use the same id twice. It makes for really nasty bugs that are difficult to squash.
You can use document.querySelector in modern browsers. document.getElementById is pretty much obsolete.
document.querySelector('#div1 #innerdiv1')
You can use classes for the inner divs instead of ids, which do not need to be unique.
The document object has a getElementById method, but the returned elements do not have this method, and it couldn't take a string that isn't exactly the id of an element [if that's what you want try a library, like jQuery or Pumbaa80's suggestion of document.querySelector].
In some browsers you can try:
document.getElementById('div1').getElementsByTagName('div')[0]
As a side note, try dropping these two html documents into html5.validator.nu or http://validator.w3.org/#validate_by_input
<!DOCTYPE html><head><title>t</title></head><body>
<div id=div1><div id=d1>one</div><div id=d2>two</div>three</div>
<div id=div2><div id=d1>four</div><div id=d2>five</div>six</div>
</body>
Now you can totally avoid using the same id twice by just using classes instead.
<!DOCTYPE html><head><title>t</title></head><body>
<div id=div1><div class=d1>one</div><div class=d2>two</div>three</div>
<div id=div2><div class=d1>four</div><div class=d2>five</div>six</div>
</body>
For the first one, you could use document.querySelector('#div2 #d1') or $('#div2 #d1')
but I don't think the result would be guaranteed across all browsers due to the fact that this should be equivalent to writing document.querySelector('#d1') which you can see returns the first occurring id that matches, or $('#d1') which returns both id matching elements in an array.
And for the second one you could use document.querySelector('#div2 .d1') or $('#div2 .d1') or the other statements for very similar results, except that your html is valid this time. You don't even have to have css that defines d1 and d2 and if you used an attribute like class="d1 mySubHeading" and class="d2 mySubHeading" you could style both with mySubHeading and leave d1 and d2 there purely for selection via these methods.
I am really new to JavaScript, and Im basically trying to build a simple Script to get information from a site like Walmart.com. Im using firebug to test my little snippets. Im having a problem getting the price.
This is the my code:
var price = document.getElementById('clearfix camelPrice');
console.log(price);
I also tried ".camelPrice" with out the period and I keep getting null.
Thanks a lot in advance!
In this case, you're using the wrong method. getElementById does exactly what it says, it gets an element by its id. Looking on Walmart.com, 'camelPrice' is a CSS class.
We can still get elements by a class. What you want is document.getElementsByClassName(). Further, you can pass multiple arguments to getElementsByClassName like so:
document.getElementsByClassName('clearfix', 'camelPrice');
This grabs all elements that have both the clearfix and camelPrice classes set.
In addition to what the others have said about your selection looking like ids, here is how you can select by class name:
document.getElementsByClassName('classname');
Newer browsers allow you to make jQuery-like selections from native JavaScript:
document.querySelectorAll('#id .classname');
http://caniuse.com/queryselector
It looks like you're trying to provide a class selector to getElementById instead of an ID selector. This is what an ID looks like:
<div id="some-id">...</div>
This is what a class looks like:
<div class="some-class">...</div>
The difference is that only one element should ever have a specific ID on a page, where many elements might have the same class.
I am not sure how you are running your JavaScript in Walmart's site, which is not impossible, but maybe you should specify it, for instance if the Walmart site is in an iframe you will not be able to use getElementById() from your site.
On the other hand if you are running some sort of local Live Editor/Console, then maybe it is possible.
For the script you show above, you have an error on the ID since an id can only be one word, and you are missing to select what type of attribute you want from the element:
For example, <input>:
var price = document.getElementById('id').value
or for other tags like <div>:
var price = document.getElementById('id').innerHTML
This is the same question as this:
Referring to a div inside a div with the same ID as another inside another
except for one thing.
The reason there are two elements with the same ID is because I'm adding rows to a table, and I'm doing that by making a hidden div with the contents of the row as a template. I make a new div, copy the innerhtml of the template to my new div, and then I just want to edit bits of it, but all the bits have the same ID as the template.
I could dynamically create the row element by element but it's a VERY complex row, and there's only a few things that need to be changed, so it's a lot easier to just copy from a template and change the few things I need to.
So how do I refer to the elements in my copy, rather than the template?
I don't want to mess up the template itself, or I'll never be able to get at the bits for a second use.
Or is there another simpler way to solve the problem?
It will probably just be easiest when manipulating the innerHtml to do a replace on the IDs for that row. Maybe something like...
var copiedRow = templateRow.innerHTML.replace(/id=/g,"$1copy")
This will make the copied divs be prefixed with "copy". You can develop this further for the case that you have multiple copies by keeping a counter and adding that count variable to the replace() call.
When you want to make a template and use it multiple times its best to make it of DOM, in a documentFragment for example.
That way it doesn't respond to document.getElementById() calls in the "live" DOM.
I made an example here: http://jsfiddle.net/PM5544/MXHRr/
id's should be unique on the page.
PM5544...
In reality, there's no use to change the ID to something unique, even though your document may not be valid.
Browsers' selector engines treat IDs pretty much the same as class names. Thus, you may use
document.querySelector('#myCopy #idToLookFor');
to get the copy.
IDs on a page are supposed to be unique, even when you clone them from a template.
If you dynamically create content on your page, then you must change the id of your newly cloned elements to something else. If you want to access all cloned elements, but not the template, you can add a class to them, so you can refer to all elements with that class:
var clonedElement = template.cloneNode(yes); // make a deep copy
clonedElement.setAttribute("id", "somethingElse"); // change the id
clonedElement.setAttribute("class",
clonedElement.getAttribute("class") + " cloned"
);
To access all cloned elements by classname, you can use the getElementsByClassName method (available in newer browsers) or look at this answer for a more in-depth solution: How to getElementByClass instead of GetElementById with Javascript?
Alternatively, if you have jQuery available, you can do this is far less lines of code:
$("#template").clone().attr("id","somethingElse")
.addClass("cloned").appendTo("#someDiv");
The class lookup is even simpler:
$(".cloned").doSomethingWithTheseElements();
Try to avoid using IDs in the child elements of the cloned structure, as all ids of the cloned element should be changed before adding the clone to the page. Instead, you can refer to the parent element using the new id and traverse the rest of the structure using classnames. Class names do not need to be unique, so you can just leave them as they are.
If you really must use ID's (or unique "name" attributes in form fields), I can strongly suggest using a framework like jQuery or Prototype to handle the DOM traversal; otherwise, it is quite a burden to resolve all the cross-browser issues. Here is an example of some changes deeper in the structure, using jQuery:
$("#template").clone().attr("id","somethingElse")
.addClass("cloned") // add a cloned class to the top element
.find("#foo").attr("id","bar").end() // find and modify a child element
.appendTo("#someDiv"); // finally, add the node to the page
Check out my ugly but functional cheese. I wrote a function that works like getelementbyid, but you give it a start node instead of the document. Works like a charm. It may be inefficient but I have great faith in the microprocessors running today's browsers' javascript engines.
function getelement(node, findid)
{
if (node)
if (node.id)
if (node.id == findid)
return node;
node = node.firstChild;
while(node)
{
var r = getelement(node, findid);
if (r != null)
return r;
node = node.nextSibling;
}
return null;
}
When you copy the row, don't you end up having a reference to it? At that point can't you change the ID?