You signed in with another tab or window. Reload to refresh your session.You signed out in another tab or window. Reload to refresh your session.You switched accounts on another tab or window. Reload to refresh your session.Dismiss alert
On the picture above, you can click on element nodes and their children will open/collapse.
45
45
```
46
46
47
-
Tags are called *element nodes* (or just elements). Nested tags become children of the enclosing ones. As a result we have a tree of elements: `<html>` is at the root, then `<head>` and `<body>` are its children etc.
47
+
Tags are called *element nodes* (or just elements). Nested tags become children of the enclosing ones. As a result we have a tree of elements: `<html>` is at the root, then `<head>` and `<body>` are its children, etc.
48
48
49
49
The text inside elements forms *text nodes*, labelled as `#text`. A text node contains only a string. It may not have children and is always a leaf of the tree.
50
50
@@ -55,15 +55,15 @@ Please note the special characters in text nodes:
55
55
- a newline: `↵` (in JavaScript known as `\n`)
56
56
- a space: `␣`
57
57
58
-
Spaces and newlines -- are totally valid characters, they form text nodes and become a part of the DOM. So, for instance, in the example above the `<head>` tag contains come spaces before `<title>`, and that text becomes a `#text` node (it contains a newline and some spaces only).
58
+
Spaces and newlines -- are totally valid characters, they form text nodes and become a part of the DOM. So, for instance, in the example above the `<head>` tag contains some spaces before `<title>`, and that text becomes a `#text` node (it contains a newline and some spaces only).
59
59
60
60
There are only two top-level exclusions:
61
61
1. Spaces and newlines before `<head>` are ignored for historical reasons,
62
-
2. If we put something after `</body>`, then that is automatically moved inside the `body`, at the end, as HTML spec requires that all content must be inside `<body>`. So there may be no spaces after `</body>`.
62
+
2. If we put something after `</body>`, then that is automatically moved inside the `body`, at the end, as the HTML spec requires that all content must be inside `<body>`. So there may be no spaces after `</body>`.
63
63
64
-
In other cases everything's honest -- if there are spaces (just like any character) in the document, then they become text nodes in DOM, and if we remove them, then there won't be any.
64
+
In other cases everything's straightforward -- if there are spaces (just like any character) in the document, then they become text nodes in DOM, and if we remove them, then there won't be any.
```smart header="Edge spaces and in-between empty text are usually hidden in tools"
82
82
Browser tools (to be covered soon) that work with DOM usually do not show spaces at the start/end of the text and empty text nodes (line-breaks) between tags.
83
83
84
-
That's because they are mainly used to decorate HTML, and do not affect (in most cases) how it is shown.
84
+
That's because they are mainly used to decorate HTML, and do not affect how it is shown (in most cases).
85
85
86
86
On further DOM pictures we'll sometimes omit them where they are irrelevant, to keep things short.
87
87
```
@@ -91,7 +91,7 @@ On further DOM pictures we'll sometimes omit them where they are irrelevant, to
91
91
92
92
If the browser encounters malformed HTML, it automatically corrects it when making DOM.
93
93
94
-
For instance, the top tag is always `<html>`. Even if it doesn't exist in the document -- it will be in DOM, the browser will create it. The same about`<body>`.
94
+
For instance, the top tag is always `<html>`. Even if it doesn't exist in the document -- it will exist in the DOM, the browser will create it. The same goes for`<body>`.
95
95
96
96
As an example, if the HTML file is a single word `"Hello"`, the browser will wrap it into `<html>` and `<body>`, add the required `<head>`, and the DOM will be:
97
97
@@ -104,7 +104,7 @@ let node3 = {"name":"HTML","nodeType":1,"children":[{"name":"HEAD","nodeType":1,
104
104
drawHtmlTree(node3, 'div.domtree', 690, 150);
105
105
</script>
106
106
107
-
While generating DOM, browser automatically processes errors in the document, closes tags and so on.
107
+
While generating the DOM, browsers automatically process errors in the document, close tags and so on.
108
108
109
109
Such an "invalid" document:
110
110
@@ -115,7 +115,7 @@ Such an "invalid" document:
115
115
<li>Dad
116
116
```
117
117
118
-
...Will become a normal DOM, as the browser read tags and restores the missing parts:
118
+
...Will become a normal DOM, as the browser reads tags and restores the missing parts:
119
119
120
120
<divclass="domtree"></div>
121
121
@@ -143,7 +143,7 @@ let node5 = {"name":"TABLE","nodeType":1,"children":[{"name":"TBODY","nodeType":
143
143
drawHtmlTree(node5, 'div.domtree', 600, 200);
144
144
</script>
145
145
146
-
You see? The `<tbody>`has appeared out of nowhere. Should keep in mind while working with tables to avoid surprises.
146
+
You see? The `<tbody>` appeared out of nowhere. You should keep this in mind while working with tables to avoid surprises.
147
147
````
148
148
149
149
## Other node types
@@ -178,7 +178,7 @@ Here we see a new tree node type -- *comment node*, labeled as `#comment`.
178
178
179
179
We may think -- why a comment is added to the DOM? It doesn't affect the visual representation in any way. But there's a rule -- if something's in HTML, then it also must be in the DOM tree.
180
180
181
-
**Everything in HTML, even comments, becomes a part of DOM.**
181
+
**Everything in HTML, even comments, becomes a part of the DOM.**
182
182
183
183
Even the `<!DOCTYPE...>` directive at the very beginning of HTML is also a DOM node. It's in the DOM tree right before `<html>`. We are not going to touch that node, we even don't draw it on diagrams for that reason, but it's there.
184
184
@@ -189,39 +189,39 @@ There are [12 node types](https://dom.spec.whatwg.org/#node). In practice we usu
189
189
1. `document` -- the "entry point" into DOM.
190
190
2. element nodes -- HTML-tags, the tree building blocks.
191
191
3. text nodes -- contain text.
192
-
4. comments -- sometimes we can put the information there, it won't be shown, but JS can read it from DOM.
192
+
4. comments -- sometimes we can put the information there, it won't be shown, but JS can read it from the DOM.
193
193
194
-
## See it yourself
194
+
## See it for yourself
195
195
196
196
To see the DOM structure in real-time, try [Live DOM Viewer](http://software.hixie.ch/utilities/js/live-dom-viewer/). Just type in the document, and it will show up DOM at an instant.
197
197
198
198
## In the browser inspector
199
199
200
-
Another way to explore DOM is to use browser developer tools. Actually, that's what we use when developing.
200
+
Another way to explore the DOM is to use the browser developer tools. Actually, that's what we use when developing.
201
201
202
-
To do so, open the web-page [elks.html](elks.html), turn on browser developer tools and switch to Elements tab.
202
+
To do so, open the web-page [elks.html](elks.html), turn on the browser developer tools and switch to the Elements tab.
203
203
204
-
Should look like this:
204
+
It should look like this:
205
205
206
206

207
207
208
208
You can see the DOM, click on elements, see their details and so on.
209
209
210
210
Please note that the DOM structure in developer tools is simplified. Text nodes are shown just as text. And there are no "blank" (space only) text nodes at all. That's fine, because most of the time we are interested in element nodes.
211
211
212
-
Clicking the <span class="devtools" style="background-position:-328px -124px"></span> button in the left-upper corner allows to choose a node from the webpage using a mouse (or other pointer devices) and "inspect" it (scroll to it in the elements tab). Works great when we have a huge HTML page and would like to see the DOM of a particular place in it.
212
+
Clicking the <span class="devtools" style="background-position:-328px -124px"></span> button in the left-upper corner allows to choose a node from the webpage using a mouse (or other pointer devices) and "inspect" it (scroll to it in the Elements tab). This works great when we have a huge HTML page (and corresponding huge DOM) and would like to see the place of a particual element in it.
213
213
214
214
Another way to do it would be just right-clicking on a webpage and selecting "Inspect" in the context menu.
215
215
216
216

217
217
218
-
At the right part of the tools there are following subtabs:
219
-
- Styles -- we can see CSS applied to the current element rule by rule, including built-in rules (gray). Almost everything can be edited at-place including the dimensions/margins/paddings of the box below.
220
-
- Computed -- to see CSS applied to the element by property: for each property we can see a rule that gives it (including CSS inheritance and such).
221
-
- Event Listeners -- to see event listeners attached to DOM elements (we'll cover them in the next part of the tutorial).
218
+
At the right part of the tools there are the following subtabs:
219
+
- **Styles** -- we can see CSS applied to the current element rule by rule, including built-in rules (gray). Almost everything can be edited in-place, including the dimensions/margins/paddings of the box below.
220
+
- **Computed** -- to see CSS applied to the element by property: for each property we can see a rule that gives it (including CSS inheritance and such).
221
+
- **Event Listeners** -- to see event listeners attached to DOM elements (we'll cover them in the next part of the tutorial).
222
222
- ...and so on.
223
223
224
-
The best way to study them is to click around. Most values are in-place editable.
224
+
The best way to study them is to click around. Most values are editable in-place.
225
225
226
226
## Interaction with console
227
227
@@ -244,7 +244,7 @@ Or we can just output it in the console and explore "at-place", like `document.b
244
244
245
245
That's for debugging purposes of course. From the next chapter on we'll access and modify DOM using JavaScript.
246
246
247
-
The browser developer tools are a great help in development: we can explore DOM, try things and see what goes wrong.
247
+
The browser developer tools are a great help in development: we can explore the DOM, try things and see what goes wrong.
248
248
249
249
## Summary
250
250
@@ -256,6 +256,6 @@ An HTML/XML document is represented inside the browser as the DOM tree.
256
256
257
257
We can use developer tools to inspect DOM and modify it manually.
258
258
259
-
Here we covered the basics, most used and important actions to start with. There's an extensive documentation about Chrome developer tools at <https://developers.google.com/web/tools/chrome-devtools>. The best way to learn the tools is to click here and there, read menus: most options are obvious. Later, when you know them in general, read the docs and pick up the rest.
259
+
Here we covered the basics, the most used and important actions to start with. There's an extensive documentation about Chrome Developer Tools at <https://developers.google.com/web/tools/chrome-devtools>. The best way to learn the tools is to click here and there, read menus: most options are obvious. Later, when you know them in general, read the docs and pick up the rest.
260
260
261
261
DOM nodes have properties and methods that allow to travel between them, modify, move around the page and more. We'll get down to them in the next chapters.
0 commit comments