I have a doubt with javascript document.write method. Mostly when I use document.write() it shows me the content written with the method in a different page. For instance, if I write the command like this, document.write("Hello, My name is Sameeksha"); then the execution of this line takes me to a different document on the same page. I want to be able to append the message on the same page, with other elements of the page. For example, if I have text boxes and buttons on the page and I want the text with document.write to appear under all the content of the page or on a particular section of a page. Please suggest what can be done to get the output in this way? As, this way it will be really easy to create dynamic HTML content.
Thank you so much for your time.
Regards,
Sameeksha Kumari
document.write is basically never used in modern Javascript.
Whan you do instead is to create explicit DOM elements and append them to the document in the place you want. For example
var x = document.createElement("div"); // Creates a new <div> node
x.textContent = "Hello, world"; // Sets the text content
document.body.appendChild(x); // Adds to the document
Instead of appending to the end you can also add child nodes to any existing node. For example:
function addChatMessage(msg) {
var chat = document.getElementById("chat"); // finds the container
var x = document.createElement("div");
x.textContent = msg;
chat.appendChild(x);
}
I'd say 6502 posted the more correct way to do it, but I think someone should mention innerHTML as well. First, give some element in your HTML body an id so you can reference it:
<div id="outputDiv">I'm empty.</div>
Then, either at the bottom of your document (at the end of the <body> tag), or any other time after the page is loaded, you can update the contents with innerHTML:
document.getElementById("outputDiv").innerHTML = "<h1>Hello!!!</h1>";
Here's a jsfiddle demonstrating this. This isn't as clean/correct/elegant as using the more standard DOM methods, but it's well supported. Sometimes quick and dirty is what you need!
Related
In tutorials I've learnt to use document.write. Now I understand that by many this is frowned upon. I've tried print(), but then it literally sends it to the printer.
So what are alternatives I should use, and why shouldn't I use document.write? Both w3schools and MDN use document.write.
The reason that your HTML is replaced is because of an evil JavaScript function: document.write().
It is most definitely "bad form." It only works with webpages if you use it on the page load; and if you use it during runtime, it will replace your entire document with the input. And if you're applying it as strict XHTML structure it's not even valid code.
the problem:
document.write writes to the document stream. Calling document.write on a closed (or loaded) document automatically calls document.open which will clear the document.
-- quote from the MDN
document.write() has two henchmen, document.open(), and document.close(). When the HTML document is loading, the document is "open". When the document has finished loading, the document has "closed". Using document.write() at this point will erase your entire (closed) HTML document and replace it with a new (open) document. This means your webpage has erased itself and started writing a new page - from scratch.
I believe document.write() causes the browser to have a performance decrease as well (correct me if I am wrong).
an example:
This example writes output to the HTML document after the page has loaded. Watch document.write()'s evil powers clear the entire document when you press the "exterminate" button:
I am an ordinary HTML page. I am innocent, and purely for informational purposes. Please do not <input type="button" onclick="document.write('This HTML page has been succesfully exterminated.')" value="exterminate"/>
me!
the alternatives:
.innerHTML This is a wonderful alternative, but this attribute has to be attached to the element where you want to put the text.
Example: document.getElementById('output1').innerHTML = 'Some text!';
.createTextNode() is the alternative recommended by the W3C.
Example: var para = document.createElement('p');
para.appendChild(document.createTextNode('Hello, '));
NOTE: This is known to have some performance decreases (slower than .innerHTML). I recommend using .innerHTML instead.
the example with the .innerHTML alternative:
I am an ordinary HTML page.
I am innocent, and purely for informational purposes.
Please do not
<input type="button" onclick="document.getElementById('output1').innerHTML = 'There was an error exterminating this page. Please replace <code>.innerHTML</code> with <code>document.write()</code> to complete extermination.';" value="exterminate"/>
me!
<p id="output1"></p>
Here is code that should replace document.write in-place:
document.write=function(s){
var scripts = document.getElementsByTagName('script');
var lastScript = scripts[scripts.length-1];
lastScript.insertAdjacentHTML("beforebegin", s);
}
You can combine insertAdjacentHTML method and document.currentScript property.
The insertAdjacentHTML() method of the Element interface parses the specified text as HTML or XML and inserts the resulting nodes into the DOM tree at a specified position:
'beforebegin': Before the element itself.
'afterbegin': Just inside the element, before its first child.
'beforeend': Just inside the element, after its last child.
'afterend': After the element itself.
The document.currentScript property returns the <script> element whose script is currently being processed. Best position will be beforebegin — new HTML will be inserted before <script> itself. To match document.write's native behavior, one would position the text afterend, but then the nodes from consecutive calls to the function aren't placed in the same order as you called them (like document.write does), but in reverse. The order in which your HTML appears is probably more important than where they're place relative to the <script> tag, hence the use of beforebegin.
document.currentScript.insertAdjacentHTML(
'beforebegin',
'This is a document.write alternative'
)
As a recommended alternative to document.write you could use DOM manipulation to directly query and add node elements to the DOM.
Just dropping a note here to say that, although using document.write is highly frowned upon due to performance concerns (synchronous DOM injection and evaluation), there is also no actual 1:1 alternative if you are using document.write to inject script tags on demand.
There are a lot of great ways to avoid having to do this (e.g. script loaders like RequireJS that manage your dependency chains) but they are more invasive and so are best used throughout the site/application.
I fail to see the problem with document.write. If you are using it before the onload event fires, as you presumably are, to build elements from structured data for instance, it is the appropriate tool to use. There is no performance advantage to using insertAdjacentHTML or explicitly adding nodes to the DOM after it has been built. I just tested it three different ways with an old script I once used to schedule incoming modem calls for a 24/7 service on a bank of 4 modems.
By the time it is finished this script creates over 3000 DOM nodes, mostly table cells. On a 7 year old PC running Firefox on Vista, this little exercise takes less than 2 seconds using document.write from a local 12kb source file and three 1px GIFs which are re-used about 2000 times. The page just pops into existence fully formed, ready to handle events.
Using insertAdjacentHTML is not a direct substitute as the browser closes tags which the script requires remain open, and takes twice as long to ultimately create a mangled page. Writing all the pieces to a string and then passing it to insertAdjacentHTML takes even longer, but at least you get the page as designed. Other options (like manually re-building the DOM one node at a time) are so ridiculous that I'm not even going there.
Sometimes document.write is the thing to use. The fact that it is one of the oldest methods in JavaScript is not a point against it, but a point in its favor - it is highly optimized code which does exactly what it was intended to do and has been doing since its inception.
It's nice to know that there are alternative post-load methods available, but it must be understood that these are intended for a different purpose entirely; namely modifying the DOM after it has been created and memory allocated to it. It is inherently more resource-intensive to use these methods if your script is intended to write the HTML from which the browser creates the DOM in the first place.
Just write it and let the browser and interpreter do the work. That's what they are there for.
PS: I just tested using an onload param in the body tag and even at this point the document is still open and document.write() functions as intended. Also, there is no perceivable performance difference between the various methods in the latest version of Firefox. Of course there is a ton of caching probably going on somewhere in the hardware/software stack, but that's the point really - let the machine do the work. It may make a difference on a cheap smartphone though. Cheers!
The question depends on what you are actually trying to do.
Usually, instead of doing document.write you can use someElement.innerHTML or better, document.createElement with an someElement.appendChild.
You can also consider using a library like jQuery and using the modification functions in there: http://api.jquery.com/category/manipulation/
This is probably the most correct, direct replacement: insertAdjacentHTML.
Try to use getElementById() or getElementsByName() to access a specific element and then to use innerHTML property:
<html>
<body>
<div id="myDiv1"></div>
<div id="myDiv2"></div>
</body>
<script type="text/javascript">
var myDiv1 = document.getElementById("myDiv1");
var myDiv2 = document.getElementById("myDiv2");
myDiv1.innerHTML = "<b>Content of 1st DIV</b>";
myDiv2.innerHTML = "<i>Content of second DIV element</i>";
</script>
</html>
Use
var documentwrite =(value, method="", display="")=>{
switch(display) {
case "block":
var x = document.createElement("p");
break;
case "inline":
var x = document.createElement("span");
break;
default:
var x = document.createElement("p");
}
var t = document.createTextNode(value);
x.appendChild(t);
if(method==""){
document.body.appendChild(x);
}
else{
document.querySelector(method).appendChild(x);
}
}
and call the function based on your requirement as below
documentwrite("My sample text"); //print value inside body
documentwrite("My sample text inside id", "#demoid", "block"); // print value inside id and display block
documentwrite("My sample text inside class", ".democlass","inline"); // print value inside class and and display inline
I'm not sure if this will work exactly, but I thought of
var docwrite = function(doc) {
document.write(doc);
};
This solved the problem with the error messages for me.
I'm making a Chrome Extension that changes the DOM of a page. But I would like to give the user an option to switch between the page before the changes and the changed page.
It's a little bit like Google translate where you can change between the orginal language and the translated message.
I could not find anything in my own searches.
I know JavaScript but not JQuery yet.
Thanks for the help.
You could save the entire body in a variable, then start overwriting things. If you want to switch back load up the old body.
You could save all the original DOM content to a variable before running the content script. You can do this by using the following code at the top of your content script:
var originalDOM = document.getElementsByTagName("*");
This saves the entire DOM in an array called originalDOM. The * acts a universal tag, requesting every tag in the document. You can read more about the .getElementsByTagName() API here.
You could try:
var html = document.getElementsByTagName("html")[0];
var page = html.innerHTML;
This will give you everything between the <html> tags.
After the content script is injected, run:
var newPage = html.innerHTML;
Now, whenever you want to switch between the pages, simply run:
html.innerHTML = page; //or newPage
You can read more about the .getElementsByTagName() API here
My code is as follows:
window.onload = initialise;
function initialise() {
var objPForSubmitMsg = document.createElement('p');
objPForSubmitMsg.setAttribute('class', 'submitmsg');
var arObjForms = document.getElementsByTagName('form');
for (i = 0; i < arObjForms.length; i++) {
var objFormParent = arObjForms[i].parentNode;
alert(objFormParent);
objFormParent.insertBefore(objPForSubmitMsg, arObjForms[i]);
}
} // end initialise().
I checked the function with alerts and it goes through.
When I "view-source" for the page after the function initialise() is done, there are no new elements added.
So my first question would be as per subject: can new elements inserted with javascript be seen with view-source?
If yes, then what is wrong with my code above? Why it doesn't insert new element?
I also tried to call initialise() from a button, but nothing happens then either.
I'm new to javascript so any comments would be appreciated.
EDIT: Thanks everyone. Ok, view-source cannot see it...
Than if I pass my page to php and load it with: $page = file_get_contents("mypage.html"); , if I echo that back with: echo $page; then I guess the newly created elements will not appear there either?
If that is the case, how would you pass the whole thing including the newly js created elements to php?
View Source in the browser shows you the original HTML source of the page - exactly what came from the server before any client side modifications have been made.
As such, it will NOT include any dynamic changes to the page made by javascript.
To see changes that have been made dynamically, use a DOM inspector. There is one built into Safari and Chrome and IE and Firebug is an add-on for Firefox. All will show you the entire DOM hierarchy, live exactly like it currently exists in the browser. In fact, you can even modify the live DOM yourself in the inspector.
Your current code is inserting an empty <p> tag which may not be visible because it's empty. If you put some content into the <p> tag, it successfully inserts one <p> tag into your page. It will only insert one because you only create one and then you try to insert the same tag before each form. You can see what your current code does here: http://jsfiddle.net/jfriend00/3fvbj7re/.
If you want a <p> tag inserted before each form in the page, you'd need to create a separate <p> tag for each insertion like this:
function initialise() {
var arObjForms = document.getElementsByTagName('form');
var objPForSubmitMsg;
for (i = 0; i < arObjForms.length; i++) {
objPForSubmitMsg = document.createElement('p');
objPForSubmitMsg.innerHTML = "hello"; // give tag some content
objPForSubmitMsg.setAttribute('class', 'submitmsg');
var objFormParent = arObjForms[i].parentNode;
objFormParent.insertBefore(objPForSubmitMsg, arObjForms[i]);
}
}
window.onload = initialise;
The Dom elements you add at runtime, were not present when the first time your page was loaded. In other words, it wasn't a part of your original page.
When you view source of your original page, it just shows the HTMl, without executing any JS or CSS, since you only explore HTMl in the source.
Hence, even when you add dynamic html elements in a page, you won't be able to see them when you click view source.
To see those elements, you should use the Developer Console of a browser.
If you want to see the current DOM you should use the code inspector (Developer Tools) or javascript console, not the source, which is what the original response body was.
In Chrome for example go to view->developer->developer tools
I would like to add that just because you can't see it with view-source, doesn't mean you can't access your newly created elements using document.getElementById('el-id') or something similar. Kinda off topic but it's important to note.
In tutorials I've learnt to use document.write. Now I understand that by many this is frowned upon. I've tried print(), but then it literally sends it to the printer.
So what are alternatives I should use, and why shouldn't I use document.write? Both w3schools and MDN use document.write.
The reason that your HTML is replaced is because of an evil JavaScript function: document.write().
It is most definitely "bad form." It only works with webpages if you use it on the page load; and if you use it during runtime, it will replace your entire document with the input. And if you're applying it as strict XHTML structure it's not even valid code.
the problem:
document.write writes to the document stream. Calling document.write on a closed (or loaded) document automatically calls document.open which will clear the document.
-- quote from the MDN
document.write() has two henchmen, document.open(), and document.close(). When the HTML document is loading, the document is "open". When the document has finished loading, the document has "closed". Using document.write() at this point will erase your entire (closed) HTML document and replace it with a new (open) document. This means your webpage has erased itself and started writing a new page - from scratch.
I believe document.write() causes the browser to have a performance decrease as well (correct me if I am wrong).
an example:
This example writes output to the HTML document after the page has loaded. Watch document.write()'s evil powers clear the entire document when you press the "exterminate" button:
I am an ordinary HTML page. I am innocent, and purely for informational purposes. Please do not <input type="button" onclick="document.write('This HTML page has been succesfully exterminated.')" value="exterminate"/>
me!
the alternatives:
.innerHTML This is a wonderful alternative, but this attribute has to be attached to the element where you want to put the text.
Example: document.getElementById('output1').innerHTML = 'Some text!';
.createTextNode() is the alternative recommended by the W3C.
Example: var para = document.createElement('p');
para.appendChild(document.createTextNode('Hello, '));
NOTE: This is known to have some performance decreases (slower than .innerHTML). I recommend using .innerHTML instead.
the example with the .innerHTML alternative:
I am an ordinary HTML page.
I am innocent, and purely for informational purposes.
Please do not
<input type="button" onclick="document.getElementById('output1').innerHTML = 'There was an error exterminating this page. Please replace <code>.innerHTML</code> with <code>document.write()</code> to complete extermination.';" value="exterminate"/>
me!
<p id="output1"></p>
Here is code that should replace document.write in-place:
document.write=function(s){
var scripts = document.getElementsByTagName('script');
var lastScript = scripts[scripts.length-1];
lastScript.insertAdjacentHTML("beforebegin", s);
}
You can combine insertAdjacentHTML method and document.currentScript property.
The insertAdjacentHTML() method of the Element interface parses the specified text as HTML or XML and inserts the resulting nodes into the DOM tree at a specified position:
'beforebegin': Before the element itself.
'afterbegin': Just inside the element, before its first child.
'beforeend': Just inside the element, after its last child.
'afterend': After the element itself.
The document.currentScript property returns the <script> element whose script is currently being processed. Best position will be beforebegin — new HTML will be inserted before <script> itself. To match document.write's native behavior, one would position the text afterend, but then the nodes from consecutive calls to the function aren't placed in the same order as you called them (like document.write does), but in reverse. The order in which your HTML appears is probably more important than where they're place relative to the <script> tag, hence the use of beforebegin.
document.currentScript.insertAdjacentHTML(
'beforebegin',
'This is a document.write alternative'
)
As a recommended alternative to document.write you could use DOM manipulation to directly query and add node elements to the DOM.
Just dropping a note here to say that, although using document.write is highly frowned upon due to performance concerns (synchronous DOM injection and evaluation), there is also no actual 1:1 alternative if you are using document.write to inject script tags on demand.
There are a lot of great ways to avoid having to do this (e.g. script loaders like RequireJS that manage your dependency chains) but they are more invasive and so are best used throughout the site/application.
I fail to see the problem with document.write. If you are using it before the onload event fires, as you presumably are, to build elements from structured data for instance, it is the appropriate tool to use. There is no performance advantage to using insertAdjacentHTML or explicitly adding nodes to the DOM after it has been built. I just tested it three different ways with an old script I once used to schedule incoming modem calls for a 24/7 service on a bank of 4 modems.
By the time it is finished this script creates over 3000 DOM nodes, mostly table cells. On a 7 year old PC running Firefox on Vista, this little exercise takes less than 2 seconds using document.write from a local 12kb source file and three 1px GIFs which are re-used about 2000 times. The page just pops into existence fully formed, ready to handle events.
Using insertAdjacentHTML is not a direct substitute as the browser closes tags which the script requires remain open, and takes twice as long to ultimately create a mangled page. Writing all the pieces to a string and then passing it to insertAdjacentHTML takes even longer, but at least you get the page as designed. Other options (like manually re-building the DOM one node at a time) are so ridiculous that I'm not even going there.
Sometimes document.write is the thing to use. The fact that it is one of the oldest methods in JavaScript is not a point against it, but a point in its favor - it is highly optimized code which does exactly what it was intended to do and has been doing since its inception.
It's nice to know that there are alternative post-load methods available, but it must be understood that these are intended for a different purpose entirely; namely modifying the DOM after it has been created and memory allocated to it. It is inherently more resource-intensive to use these methods if your script is intended to write the HTML from which the browser creates the DOM in the first place.
Just write it and let the browser and interpreter do the work. That's what they are there for.
PS: I just tested using an onload param in the body tag and even at this point the document is still open and document.write() functions as intended. Also, there is no perceivable performance difference between the various methods in the latest version of Firefox. Of course there is a ton of caching probably going on somewhere in the hardware/software stack, but that's the point really - let the machine do the work. It may make a difference on a cheap smartphone though. Cheers!
The question depends on what you are actually trying to do.
Usually, instead of doing document.write you can use someElement.innerHTML or better, document.createElement with an someElement.appendChild.
You can also consider using a library like jQuery and using the modification functions in there: http://api.jquery.com/category/manipulation/
This is probably the most correct, direct replacement: insertAdjacentHTML.
Try to use getElementById() or getElementsByName() to access a specific element and then to use innerHTML property:
<html>
<body>
<div id="myDiv1"></div>
<div id="myDiv2"></div>
</body>
<script type="text/javascript">
var myDiv1 = document.getElementById("myDiv1");
var myDiv2 = document.getElementById("myDiv2");
myDiv1.innerHTML = "<b>Content of 1st DIV</b>";
myDiv2.innerHTML = "<i>Content of second DIV element</i>";
</script>
</html>
Use
var documentwrite =(value, method="", display="")=>{
switch(display) {
case "block":
var x = document.createElement("p");
break;
case "inline":
var x = document.createElement("span");
break;
default:
var x = document.createElement("p");
}
var t = document.createTextNode(value);
x.appendChild(t);
if(method==""){
document.body.appendChild(x);
}
else{
document.querySelector(method).appendChild(x);
}
}
and call the function based on your requirement as below
documentwrite("My sample text"); //print value inside body
documentwrite("My sample text inside id", "#demoid", "block"); // print value inside id and display block
documentwrite("My sample text inside class", ".democlass","inline"); // print value inside class and and display inline
I'm not sure if this will work exactly, but I thought of
var docwrite = function(doc) {
document.write(doc);
};
This solved the problem with the error messages for me.
I've created a JavaScript script that can be pasted on someone's page to create an iFrame. I would like for the person to be able to paste the script where they would like the iFrame to appear.
However, I can't figure out how to append the DOM created iFrame to the location where the script has been pasted. It always appends it to the very bottom of the body.
How do I append in place?
Mm. You could do:
document.write("<div id='iframecontainer'></div>");
document.getElementById('iframecontainer').innerHTML = '...';
But that feels ugly/wrong in a lot of different levels. I am not aware of any other alternatives, though.
EDIT: Actually, a quick google search revealed this artlcle which discusses why document.write is ugly and a nice alternative for the particular pickle you're in: Give your script tag an ID!
<script id="iframeinserter" src=".."></script>
And then you can get a reference to the script tag and insert the iframe before it:
var newcontent = document.createElement('iframe');
var scr = document.getElementById('iframeinserter');
scr.parentNode.insertBefore(newcontent, scr);
Paulo's answer can also be done without the ID, by simply looking for the last <script> element. This must be the script block we're in, because JavaScript guarantees all content past the closing tag of the current script block has not yet been parsed(*):
var scripts= document.getElementsByTagName('script');
var script= scripts[scripts.length-1];
script.parentNode.insertBefore(d, script);
This can be put in an onload/ready function if you like, but if so the ‘var script’ must be calculated at include-time and not in the ready function (when that executes, more <script>s will have been parsed).
(*: except in the case of <script defer>.)
If the user can give an id of an element that will be where the iframe should be, then it would be possible to just use css to move the iframe to where it should be on the page.