In this snippet, …args is called the “rest arguments” — as the name implies, this contains the rest of the arguments. Used inside a function, this refers to the current object. What that actually means is specified by the way in which you called that function. If you called it using dot notation or bracket notation on an object, that object becomes this. If dot notation wasn’t used for the call, this refers to the global object. In the above code, the variable args holds all the values that were passed into the function.
For a more detailed explanation of each of these topics, check out the rest of the documentation. To learn more about defining components, check out the React.Component API reference. Clicking any of the list item’s buttons throws an error because the jumpTo method is undefined.
The main benefit of immutability is that it helps you build pure components in React. Immutable data can easily determine if changes have been made, which helps to determine when a component requires re-rendering. In the previous code example, we suggested that you create a copy of the squares array using the slice() method instead of modifying the existing array. We’ll now discuss immutability and why immutability is important to learn. After these changes, we’re again able to click on the Squares to fill them, the same as we had before.
Section 5 Functions
- This allows you to build data structures of arbitrary complexity.
- Create a variable called carName and assign the value Volvo to it.
- Map – introduce you to the Map type that holds a collection of key-value pairs.
- Promise.allSettled() – accept a list of promises and returns a new promise that resolves to an array of values, which were settled by the input promises.
- If…else – learn how to execute a block of code based on a specified condition.
- Just like the name goes – form validation – checks and validates whether or not the provided information or data is accurate or not.
Add a file named index.js in the src/ folder with this JS code. Add a file named index.css in the src/ folder with this CSS code. You don’t have to complete all of the sections at once to get the value out of this tutorial. Try to get as far as you can — even if it’s one or two sections.
- Own Properties – understand the own and inherited properties.
- Should the user leave the site and return later, we will save the message using the Web Storage API. We will also include an option to change the user, and therefore, the welcome message.