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MongoDB provides text indexes to support text search queries on string content. text indexes can include any field whose value is a string or an array of string elements.
0:00 - intro ( Listening will help for today's context )
2:09 - explaining behavior, how it is created? Advantages we have ( introducing text index )
8:39 - Restrictions and Performance
13:32 Additional Properties
15:38 Overview of How I implemented and how it giving the result? ( Discuss it next part too broadly )
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In the previous chapters you've learnt how to select individual elements on a web page. But there are many occasions where you need to access a child, parent or ancestor element. See the JavaScript DOM nodes chapter to understand the logical relationships between the nodes in a DOM tree.
DOM node provides several properties and methods that allow you to navigate or traverse through the tree structure of the DOM and make changes very easily. In the following section we will learn how to navigate up, down, and sideways in the DOM tree using JavaScript.
You can use the firstChild
and lastChild
properties of the DOM node to access the first and last direct child node of a node, respectively. If the node doesn't have any child element, it returns null
.
<div id="main">
<h1 id="title">My Heading</h1>
<p id="hint"><span>This is some text.</span></p>
</div>
<script>
var main = document.getElementById("main");
console.log(main.firstChild.nodeName); // Prints: #text
var hint = document.getElementById("hint");
console.log(hint.firstChild.nodeName); // Prints: SPAN
</script>
Note: The
nodeName
is a read-only property that returns the name of the current node as a string. For example, it returns the tag name for element node,#text
for text node,#comment
for comment node,#document
for document node, and so on.
If you notice the above example, the nodeName
of the first-child node of the main DIV element returns #text instead of H1. Because, whitespace such as spaces, tabs, newlines, etc. are valid characters and they form #text nodes and become a part of the DOM tree. Therefore, since the <div>
tag contains a newline before the <h1>
tag, so it will create a #text node.
To avoid the issue with firstChild
and lastChild
returning #text or #comment nodes, you could alternatively use the firstElementChild
and lastElementChild
properties to return only the first and last element node, respectively. But, it will not work in IE 9 and earlier.
<div id="main">
<h1 id="title">My Heading</h1>
<p id="hint"><span>This is some text.</span></p>
</div>
<script>
var main = document.getElementById("main");
alert(main.firstElementChild.nodeName); // Outputs: H1
main.firstElementChild.style.color = "red";
var hint = document.getElementById("hint");
alert(hint.firstElementChild.nodeName); // Outputs: SPAN
hint.firstElementChild.style.color = "blue";
</script>
Similarly, you can use the childNodes
property to access all child nodes of a given element, where the first child node is assigned index 0. Here's an example:
<div id="main">
<h1 id="title">My Heading</h1>
<p id="hint"><span>This is some text.</span></p>
</div>
<script>
var main = document.getElementById("main");
// First check that the element has child nodes
if(main.hasChildNodes()) {
var nodes = main.childNodes;
// Loop through node list and display node name
for(var i = 0; i < nodes.length; i++) {
alert(nodes[i].nodeName);
}
}
</script>
The childNodes
returns all child nodes, including non-element nodes like text and comment nodes. To get a collection of only elements, use children
property instead.
<div id="main">
<h1 id="title">My Heading</h1>
<p id="hint"><span>This is some text.</span></p>
</div>
<script>
var main = document.getElementById("main");
// First check that the element has child nodes
if(main.hasChildNodes()) {
var nodes = main.children;
// Loop through node list and display node name
for(var i = 0; i < nodes.length; i++) {
alert(nodes[i].nodeName);
}
}
</script>
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