- Quick sidebar, so far you've seen me use dot notation to gain access to properties inside objects. First, we mentioned objects, say course. We put a dot in to tell JavaScript we are looking for a property inside course and then we just list out property, title. We can also use bracket notation to do the exact same thing. Again we list out the object first, course.
Then we set up a square bracket and inside the square bracket we quote the title. This gives us the same result, the property inside the object. So why do we have these two different notations to do the same thing? It has a very specific use. In some cases, when you work with objects they come from somewhere else, let's say PHP or they're just generated from a data set. And the property names may be a little odd.
For instance, they may have operators inside them. So an object that I've had to work with previously had this notation for a property, WP:image. Now if I try to use dot notation to get at this property something weird happens. So I say course.WP. And then JavaScript sees the colon and says "that's an operator", image.
And it goes "I don't understand what you're trying to do here but you broke your property so heres an error for you." That means I cannot get at this property. This is where bracket notation comes in. When we use bracket notation, we put the property title in a quote, thereby making it a string and that means that JavaScript will not try to parse this operator into something else so it'll work. We say course, square bracket, "WP:image", and everything works fine.
Dot notation works well for properly named properties. Bracket notation works well for when we might have to convert the property name into a string. You can use these both at any time to do the same thing and you can mix them inside the code. You don't have to choose one over the other. But you have the option and any time you encounter something weird like WP:image remember bracket notation is there to solve your problem.
Author
Updated
4/1/2019Released
5/17/2017Through practical examples and mini-projects, this course helps you build your understanding of JavaScript piece by piece, from core principles like variables, data types, conditionals, and functions through advanced topics including loops, closures, and DOM scripting. Along the way, you will also be introduced to some ES6 and the basics of JavaScript libraries.
- What is JavaScript?
- Working with data
- Using functions and objects
- Working with JavaScript and the DOM
- Changing DOM elements
- Handling events
- Working with loops
- Making images responsive using markup
- Troubleshooting code
- Validating functionality
- Minifying JavaScript
Skill Level Beginner
Duration
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Introduction
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Welcome1m 7s
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1. JavaScript: An Introduction
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What is JavaScript?2m 38s
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2. The Basics
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Introducing the browser console10m 31s
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3. Working with data
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Data types in JavaScript4m 2s
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Arrays2m 20s
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4. Functions and Objects
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Functions in JavaScript3m 28s
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Anonymous functions5m 11s
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Object constructors6m 16s
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Closures8m 11s
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5. JavaScript and the DOM, Part 1: Changing DOM Elements
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Access and change elements4m 33s
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Access and change classes3m 45s
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Access and change attributes4m 53s
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Add DOM elements6m 56s
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6. Project: Create an Analog Clock
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Use CSS to move clock hands3m 49s
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7. JavaScript and the DOM, Part 2: Events
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What are DOM events?1m 31s
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Some typical DOM events1m 59s
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Add and use event listeners6m 51s
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8. Project: Typing Speed Tester
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Add a reset button5m 3s
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Loops3m 37s
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Looping through arrays4m 7s
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Break and continue loops7m 9s
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10. Project: Automated Responsive Images Markup
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Project breakdown1m 55s
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Rundown of project setup3m 26s
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11. Troubleshooting, Validating, and Minifying JavaScript
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Troubleshooting JavaScript7m 20s
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Online script linting5m 57s
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Automate script linting8m 24s
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Online script minification2m 50s
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Automate script minification2m 24s
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12. Bonus Chapter: Ask the Instructor
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What are arrow functions?3m 11s
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What does the % symbol do?3m 47s
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Conclusion
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Next Steps1m 55s
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Video: Sidebar: Dot and bracket notation