HTML5 Node cheat sheet: 21 APIs you should know in 2020

This quick HTML Node guide will cover 21 of the most popular and widely used APIs in the HTML DOM Node:

getElementById(id)
getElementsByClassName(className)
getElementsByTagName(tagName)
getSelection()
getElementsByName and querySelector(selector)
querySelectorAll(selector)
parentNode.insertBefore(newNode, refNode)
appendChild(node)
createElement(elementName)
createTextNode(textString)
removeChild(childNode)
replaceChild(newNode, childNode)
setAttribute(attrKey, attrValue)
getAttribute(attrKey)
getAttributeNames()
cloneNode()
classList
parentNode
parentElement
innerHTML
innerText

Every developer should have these APIs at their fingertips before taking on web frameworks. Mastering them is the best way to build a foundational understanding of when and how to use the frameworks.

Let’s dive in.

1. `getElementById(id)`

getElementById(id) returns the Node instance of an element by its id attribute.

<div id="div1">Div 1</div>
<p id="par1">I'm a Paragraph</p>

To get the DOM instance of 1 using the getElementById method, pass its ID, div1, to the method.

const div1Node = document.getElementById("div1")

div1Node is an object or instance of HTMLDivElement.

To get the DOM instance of I'm a Paragraph, pass its ID, par1.

const par1Node = document.getElementById("par1")

par1Node is an object or instance of HTMLParagraphElement.

With these instances, we can manipulate or perform actions on the elements.

2. `getElementsByClassName(className)`

This method returns a collection (HTMLCollection) of DOM nodes whose attribute class value is equal to the className string.

<div class="tab-body">
    <div class="tab-content tab-active">
        Div 1
    </div>        
    <div class="tab-content">
        Div 2
    </div>
    <div class="tab-content">
        Div 3
    </div>
</div>

We have divs with the attribute class names tab-body, tab-content, and tab-active. All of these are class names. A class name is the value of the class attribute set on an element.

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To get the DOM Nodes of the divs with class name tab-content, call the getElementsByClassName() method by passing tab-content as arg.

>> document.getElementsByClassName("tab-content")

// HTMLCollection
0: <div class="tab-content tab-active">
1: <div class="tab-content">
2: <div class="tab-content">
length: 3

As you can see, it returns a collection of the divs. It is actually an array because we can refer to them using number-index. As you might guess, the first element is Div 1, the second element is Div 2, and the third element is Div 3.

3. `getElementsByTagName(tagName)`

This will return a collection of DOM nodes whose tag name(element name) is equal to the tagName string specified.

The tag name will consist of names of the elements, such as div, p, img, video, b, i, br, button, input, etc.

<div>
    Div 1
</div>        
<div>
    Div 2
</div>        

<p>
    I'm Paragraph 1
</p>
<p>
    I'm Paragraph 2
</p>

<button>Button 1</button>
<button>Button 2</button>

If you call getElementsByTagName() with arg, it will return the divs in the HTML.

document.getElementsByTagName("div")

// HTMLCollection
0: <div> Div 1
1: <div> Div 2
length: 2

Passing p returns all paragraph elements.

document.getElementsByTagName("p")

// HTMLCollection
0: <p> I'm Paragraph 1
1: <p> I'm Paragraph 2
length: 2

Passing button returns all button elements.

4. `getSelection()`

This method returns the text node of the text selected in a document. This selected text area is the area highlighted in the document using the mouse or by the finger in a touch screen.

This method returns Selection. This object has an anchorNode property whose value is the text node of the text highlighted.

<div>I'm Div1</div>

If you highlight I'm Div1, document.getSlection() will return the object.

document.getSelection()

// Selection
//    anchorNode: #text
//    ...

The anchorNode is a text node whose nodeValue is Div1, the highlighted text.

// TODO: Complete this.

5. `getElementsByName` and `querySelector(selector)`

This method will return the first occurrence of the DOM node with the selector string specified.

The selector string could be an:

Element name(or tag name)
Class name
ID name

Let’s zoom in on each scenario.

Element or tag name

The selector will be the element’s name.

<div>
    Div 1
</div>        
<div>
    Div 2
</div>
<div>
    Div 3
</div>

document.querySelector("div")

>> div Div 1

It will return the first occurance of the div element — in this case, Div 1.

Class name

To get by the element’s attribute class name, the class name arg is prefixed with a dot ..

<div class="tab div1">
    Div 1
</div>        
<div class="tab div2">
    Div 2
</div>
<div class="div3">
    Div 3
</div>

To get div with class div1:

document.querySelector(".div1")

>> div Div 1

We started with a dot (.) and then the class name.

To get div with class div2:

document.querySelector(".div2")

>> div Div 2

If you pass .tab, there are two divs with tab class names. Only the first div is returned.

document.querySelector(".tab")

>> div Div 1

ID name

To get an element with its IS name, prefix the ID name arg with a hash #.

<div id="div1">
    Div 1
</div>        
<div id="div2">
    Div 2
</div>
<div id="div3">
    Div 3
</div>

To get the div with id “div1”:

document.querySelector("#div1")

Note the use of the hash #. We started with the # followed by the ID name.

This returns the divDiv 1.

6. `querySelectorAll(selector)`

This will return the NodeList of all occurrences of the selector in a document.

Again, the selector could be an:

Element name
Class name
ID name

Element name

<div>
    Div 1
</div>        
<div>
    Div 2
</div>
<div>
    Div 3
</div>
<p>
    I'm Paragraph 1
</p>
<p>
    I'm Paragraph 2
</p>

To select all divs, pass div to the method.

document.querySelectorAll("div")

// NodeList(3)
//  0: div Div 1
//  1: div Div 2
//  2: div Div 3

It returns a NodeList of all the divs. NodeList is like an array, so you can refer to the elements by index.

Once again, the first element is Div 1, the second is Div 2, and the third is Div 3.

Class name

Query the elements by their class names.

<div class="tab div1">
    Div 1
</div>        
<div class="div2">
    Div 2
</div>
<p class="tab par1">
    I'm Paragraph
</p>

To query elements with the class name tab, pass .tab (a dot followed by the class name).

document.querySelectorAll(".tab")

// NodeList(2)
//  0: div Div 1
//  1: p I'm Paragraph

It returns the Div 1 and I'm Paragraph elements because they have the class name tab.

ID name

This queries elements with a specified id attribute value. The arg starts with a hash (#) followed immediately by the ID name.

In this case, ids are unique. If you assign the same id value to more than one element, the browser will take the first element and ignore the rest. Using getElementById returns null on ids with values assigned to multiple elements. But using this querySelectorAll returns all the elements with the specified id value.

<div class="div1" id="tab">
    Div 1
</div>        
<div class="div2" id="tab">
    Div 2
</div>
<p class="tab par1" id="par1">
    I'm Paragraph
</p>

To get the elements with tab ids:

document.querySelectorAll("#tab")

// NodeList(2)
//  0: div Div 1
//  1: div Div 2

Div 1 and Div 2 are returned because they have the ID tab.

7. `parentNode.insertBefore(newNode, refNode)`

This method places a Node before a child Node refNode in a parentNode. The newNode is followed immediately by the refNode, all are children of the parentNode.

<div id="parent">
    Parent Node
    <div id="child">Child Node</div>
</div>

To place an element before the #child, use the insertBefore method.

const newNode = document.createElement("b")
newNode.appendChild(document.createTextNode("Bold Child Node"))

parent.insertBefore(newNode, child)

Here we created a b bold element with text node Bold Child Node and used the insertBefore method to insert it before the #child node in the #parent.

The HTML looks like this:

<div id="parent">
    Parent Node
    <b>Bold Child Node</b>
    <div id="child">Child Node</div>
</div>

If you refer to an existing Node in the DOM, the Node will be removed from its position and placed in the new position.

<div>
    Other Node
    <div id="othernode">
        Other Node Child
    </div>
</div>

<div id="parent">
    Parent Node
    <div id="child">Child Node</div>
</div>

We want to use insertBefore to insert #othernode to #parent before its child #child.

parent.insertBefore(othernode, child)

This removes #othernode from its parent node Other Node and places it inside #parent before its #child node.

The outcome:

<div>
    Other Node
</div>

<div id="parent">
    Parent Node
    <div id="othernode">
        Other Node Child
    </div>
    <div id="child">Child Node</div>
</div>

8. `appendChild(node)`

This method adds a node to an element as its last child element.

<div id="divNode">
    <div>Div Node Child</div>
    <div>Div Node Child</div>
    <p>Paragraph Node Child</p>
</div>

To append a p element to the #divNode using appendChild:

const pEl = document.createElement("p")
pEl.append(createTextNode("Paragraph Node Child"))

divNode.appendChild(pEl)

The outcome:

<div id="divNode">
    <div>Div Node Child</div>
    <div>Div Node Child</div>
    <p>Paragraph Node Child</p>
    <p>Paragraph Node Child</p>    
</div>

A new p Node is added to the end of the #divNode.

If the node is an existing node in the document, it will be removed from its position.

<p id="pNode">Paragraph Node</p>    

<div id="divNode">
    <div>Div Node Child</div>
    <div>Div Node Child</div>
    <p>Div Node Child</p>
</div>

Appending p#pNode to #divNode will remove p#pNode from its original position.

divNode.appendChild(pNode)

The outcome:

<div id="divNode">
    <div>Div Node Child</div>
    <div>Div Node Child</div>
    <p>Div Node Child</p>
    <p id="pNode">Paragraph Node</p>    
</div>

9. `createElement(elementName)`

This method creates the Node of the element specified. The elementName arg is a string value of the element Node to be created.

To create a div Nod, pass div. A button node will be "button", etc.

const divNode = document.createElement("div")
const buttonNode = document.createElement("button")

divNode will be an HTMLDivElement object. buttonNode will be an HTMLButtonElement object.

All element nodes created from this have a base inheritance from HTMLElement.

divNode instanceof HTMLDivElement
>> true

divNode instanceof HTMLElement
>> true

buttonNode instanceof HTMLButtonElement
>> true

buttonNode instanceof HTMLElement
>> true

The element nodes returned are used to manipulate and perform actions on the node and its children.

10. `createTextNode(textString)`

This method creates a Text node. A Text node is used to represent a place in the DOM or element where text will be placed.

To place text in an element, you must first create a Text node by calling createTextNode with the text string as arg and then appending the text node to the element.

<div id="parentNode">
    <div>Child Node</div>
</div>

To place a text in #parentNode:

parentNode.appendChild(document.createTextNode("Text"))

The outcome:

<div id="parentNode">
    <div>Child Node</div>
    Text
</div>

11. `removeChild(childNode)`

This removes a child node and its children from a node.

<div id="parentNode">
    <div id="childNode1">Child Node 1</div>
    <div id="childNode2">Child Node 2</div>
    <div id="childNode3">Child Node 3</div>
</div>

To remove #childNode1 from #parentNode:

parentNode.removeChild(childNode1)

The outcome:

<div id="parentNode">
    <div id="childNode2">Child Node 2</div>
    <div id="childNode3">Child Node 3</div>
</div>

The node to be removed must be a child node of the reference node. Trying to remove a node that is not a child of the specified node will throw a NotFoundError.

NotFoundError: Node.removeChild: The node to be removed is not a child of this node

Trying to remove something that is nonexistent will throw ReferenceError.

ReferenceError: childNode11 is not defined

12. `replaceChild(newNode, childNode)`

This method replaces a child node in a parent node with the specified node.

The newNode is the node to replace the chidlNode of the parent node.

The newNode to replace the childNode can be a child node of the parent node.

<div id="node">Node 1</div>

<div id="parentNode">
    <div id="childNode2">Child Node 2</div>
    <div id="childNode3">Child Node 3</div>
</div>

To replace #childNode2 in #parentNode with #node:

parentNode.replaceChild(node, childNode2)

The outcome:

<div id="parentNode">
    <div id="node">Node 1</div>
    <div id="childNode3">Child Node 3</div>
</div>

#node is removed from its original position and replaced with the #childNode2 in its position inside the #parent.

<div id="parentNode">
    <div id="childNode1">Child Node 1</div>
    <div id="childNode2">Child Node 2</div>
    <div id="childNode3">Child Node 3</div>
</div>

You can replace #childNode2 with #childNode1.

parentNode.replaceChild(childNode1, childNode2)

The outcome:

<div id="parentNode">
    <div id="childNode1">Child Node 1</div>
    <div id="childNode3">Child Node 3</div>
</div>

13. `setAttribute(attrKey, attrValue)`

This method sets an attribute to an element. attrKey is the attribute name and attrValue is the value of the attribute.

<div id="divNode">Div </div>

To set a class attribute to #divNode with a value of panel using setAttribute:

divNode.setAttribute("class", "panel")

The outcome will be:

<div id="divNode" class="panel">Div</div>

You can set multiple values to an attribute by separating the string with space.

divNode.setAttribute("class", "panel panel-group")

This will set the class attribute with the value panel panel-group.

<div id="divNode" class="panel panel-group">Div</div>

14. `getAttribute(attrKey)`

This method returns the value of an attribute.

Given an element:

<div id="divNode" class="panel panel-group">Div</div>

To get the value of the id attribute in #divNode:

divNode.getAttribute("id")

// divNode

To get the values of the class attribute:

divNode.getAttribute("class")

// "panel panel-group"

15. `getAttributeNames()`

This methods returns in an array all the attibutes in an element.

<div id="divNode" class="panel panel-group">Div</div>

To get all the attributes defined in the div node:

divNode.getAttributeNames()

// Array[ "id", "class" ]

16. `cloneNode()`

This method clones or replicates a DOM node. It creates another reference of a DOM node so the original is not touched.

This is often used in DOM APIs to remove DOM nodes, such as appendChild, replaceChild, etc. These APIs remove the DOM node they are acting on, so if you don’t want the DOM node to be removed, clone the DOM node so the API works on a clone of it without affecting the original copy.

Note: cloneNode doesn’t clone the element’s child nodes. It just copies the element alone.

For example, let’s say you have a DOM node that you want to append to another DOM node.

<div id="div1Node">
    Div 1
</div>

<div id="div2Node">
    Div 2
</div>

If you want to append #div1Node to #div2Node without affecting #div1Node‘s position (i.e., without removing it from its position), you can clone it using cloneNode and pass the cloned node to the appendChild method.

div2Node.appendChild(div1Node.cloneNode())

The outcome:

<div id="div1Node">
    Div 1
</div>

<div id="div2Node">
    Div 2
    <div id="div1Node"></div>
</div>

#div1Node is appended to #div2Node but without its child text node.

To clone a node with its whole children subtree, pass the boolean true to cloneNode.

div2Node.appendChild(div1Node.cloneNode(true))

This will copy the #div1Node with its Text child and append them to #div2Node

<div id="div1Node">
    Div 1
</div>

<div id="div2Node">
    Div 2
    <div id="div1Node">
        Div 1
    </div>
</div>

17. `classList`

This is a property in DOM nodes with an array value. The array contains the values of the class name in an element.

<div id="divNode" class="panel panel-group item"></div>

The classList on #divNode will be:

divNode.classList

// DOMTokenList [ "panel", "pane-group", "item" ]

This DOMTokenList is a subclass of DOMTokenListPrototype, which contains methods used to manipulate class name values in an element.

`add`

This adds a new value to an element’s class name.

<div id="divNode" class="panel panel-group item"></div>

To add “item-group” to #divNode class attribute:

divNode.classList.add("item-group")

<div id="divNode" class="panel panel-group item item-group"></div>

`contains`

Checks whether the class name has a specified value.

<div id="divNode" class="panel panel-group item"></div>

To check if the #divNode’s class attribute has “panel”. We do this:

divNode.classList.contains("panel")

// true

`item(index)`

To retrieve a class value from the list using index style.

For example:

<div id="divNode" class="panel panel-group item"></div>

divNode.classList.item(0) will be panel
divNode.classList.item(1) will be panel-group
divNode.classList.item(2) will be item

`remove`

This removes a class value from the attribute.

For example:

<div id="divNode" class="panel panel-group item"></div>

To remove a panel from the #divNode‘s class name:

divNode.classList.remove("panel")

Outcome:

<div id="divNode" class="panel-group item"></div>

`replace`

This replaces a class value in the list with a new value.

For example:

<div id="divNode" class="panel panel-group item"></div>

To replace “item” in divNode class names with “tab”, we do this:

divNode.classList.replace("item", "tab")

Outcome:

<div id="divNode" class="panel panel-group tab"></div>

`toggle`

This method removes or adds a specified value to the class names.

If the class name is not in the element, it adds it. If the class name is in the element, it removes it. That’s toggling.

<div id="divNode" class="panel panel-group item"></div>

We can remove/add the “panel” class name, like this:

Example No. 1

divNode.classList.toggle("panel")

Outcome:

<div id="divNode" class="panel-group item"></div>

Example No. 2

divNode.classList.toggle("panel")

Outcome:

<div id="divNode" class="panel panel-group item"></div>

Example No. 3

divNode.classList.toggle("panel")

Outcome:

<div id="divNode" class="panel-group item"></div>

18. `parentNode`

This returns the DOM node instance of an element’s parent node.

<div id="divNode">
    Parent Node
    <div id="divChildNode"></div>
</div>

To get the parent node of the #divChildNode:

divChildNode.parentNode

// div ParentNode

19. `parentElement`

See above; this works the same as parentNode.

20. `innerHTML`

This returns the HTML markup of an element.

For example:

<div id="divNode">
    <p>I'm Paragraph</p>
    <div id="childNode1">Chidl Node 1</div>
    <div id="childNode2">Child Node 2</div>
    <div id="childNode3">Child Node 3</div>
</div>

The innerHTML of #divNode would be:

divNode.innerHTML

// "\n    <p>I'm Paragraph</p>\n    <div id=\"childNode1\">Chidl Node 1</div>\n    <div id=\"childNode2\">Child Node 2</div>\n    <div id=\"childNode3\">Child Node 3</div>\n"

It is a string representation of the child nodes of the #divNode element.

innerHTML is used to build up DOM nodes by concatenating two or more HTML markup strings.

For example:

<div id="divNode">
    Div 1
<div>

To add the HTML markup I'm Paragraph to divNode:

divNode.innerHTML += "<p>I'm Paragraph</p>"

The DOM outcome will be as follows.

<div id="divNode">
    Div 1
    <p>I'm Paragraph</p>
<div>

To prepend it before the divNode HTML:

divNode.innerHTL = "<p>I'm Paragraph</p>" + divNode.innerHTML

21. `innerText`

This returns the text nodes of an element’s children nodes.

For example:

<div id="divNode">
    <p>I'm Paragraph</p>
    <div id="childNode1">Chidl Node 1</div>
    <div id="childNode2">Child Node 2</div>
    <div id="childNode3">Child Node 3</div>
</div>

innerText on divNode returns in a string all the text nodes contained in the #divNode. It will run down to its last subtree and collect all the text nodes there.

divNode.innerText

// "I'm Paragraph\n\nChidl Node 1\nChild Node 2\nChild Node 3"

Conclusion

If you have any questions regarding the APIs outlined above or suggestions about anything I should add, correct, or remove, feel free to comment, shoot me an email, or DM me.

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