Traversing the DOM
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Getting all Elements with the same class
var elements = document.querySelectorAll('.box');
// the queryelectorall Returns a Node List so we have to convert it to a regular array by using the slice.call
var boxesArr = Array.prototype.slice.call(elements);
boxesArr.forEach(function(curr){
cur.style.backgroundColor = 'green';
});
ES6 Version
const boxesArr = Array.from(elements) boxesArr.forEach(cur => cur.style.backgroundColor = 'blue');
Selecting Elements with the query selector
document.querySelector('h1');
document.querySelector('.classname'); // will return the 1st item with that class name
document.querySelectorAll('.classname'); // will return a array with all items with that class name
document.querySelectorAll(.classname').[0] // will select the first array item with that classname
document.querySelector('#idname');
Creating and Inserting Elements
This will append the text after the first li
var p = document.createElement('P');
p.textContent = "A new Paragraph";
p.style.fontSize = '17px';
var li= document.querySelector('li');
li.appendChild(p);
This will append the text after the second li
var p = document.createElement('P');
p.textContent = "A new Paragraph";
p.style.fontSize = '17px';
var li= document.querySelectorAll('li')[1];
li.appendChild(p);
HTML
<body>
<h1>Outwter</h1>
<ul>
<li><a href="#">Link 1</a></li>
<li><a href="#">Link 2</a></li>
</ul>
</body>
Changing CSS
NOTE: CSS style names and DOM Styles are a little Different. eg. css background color is background-color while DOM is backgorundColor
var mystyle = document.querySelector('#myid');
mystyle.style.backgroundColor = "red";