Ngfor angular

NgFor is a structural directive, meaning that it changes the structure of the DOM, ngfor angular. Sometimes we also want to get the index of the item in the array we are iterating over.

In this example, we are creating an item using the let keyword of the friendlist array. It will iterate over each item in the array, and will print out the item name and item age, or any other object key we have in the array object. You will see the above output when you save. That is because we have 8 items in the array. So, we we get 8 items in our list tag. But it is static data, so let's change it to dynamic. Here, we are using item.

Ngfor angular

In this post we are going to go over the ngFor core directive, namely we are going to go over the following:. So let's get started diving into ngFor! Below you can also find a video version of this post if you prefer, and the running code of this post is available here. Note: If instead of ngIf you are looking for the for syntax, then check my other guide instead: Angular for: Complete Guide. The core directive ngFor allows us to build data presentation lists and tables in our HTML templates. Let's take for example the following data:. With ngFor we can print this data to the screen under the form of a data table, by generating HTML similar to this:. This template will generate the HTML table that we showed just above. We can see in this example the most common syntax for using ngFor :. Note that the loop variable hero is only visible inside the loop, you would not be able to access it outside the ngFor section.

Let's say we are calling an API.

.

Note : In this Angular 9 tutorial , we'll be learning about the ngFor directive by building a simple example that fetches data and displays it in the HTML template. This is similar to the loop constructs in programming languages. Check out how to install Angular 9 and generate a project. For example, this is an example template:. The let and of keywords are mandatory in the ngFor expression. In many scenarios, you would need to know about the index of the current element inside the ngFor loop.

Ngfor angular

We will discover, how we can use the ngFor directive to display multiple elements directly from a JavaScript array. Also, we will take a look at the utilities of the ngFor directive, like the index, or even and odd. When we got the basics, we will move on to some more advanced topics like change-detection and DOM manipulation to tweak the performance of our for-loop using trackBy. We can use this directive, if we want to display a dynamic list, for example, an array of elements on the screen. This array could look like this example data:.

Jellyfish launcher

So although we can use it programmatically in the component class, we can also pass it directly to ngFor and iterate over it directly. And if you would like to know about more advanced Angular Core features like ngFor, we recommend checking the Angular Core Deep Dive course, where we cover all the Angular core directives in great detail. Do you see what happened here? We can get the index of the current element by using the index variable:. Let's take for example the following data:. This is called interpolation, and it's how we show data in the HTML template. Let's say that you are shipping to ancient mobile browsers or ancient versions of IE: you might want to consider applying trackBy as a precaution in your larger tables, but it really depends on your system and the use case. So, if the value is true, it will change to false. We use the NgFor directive to loop over an array of items and create multiple elements dynamically from a template element. And while I am not coding, I enjoy writing poetry and stories, playing the piano, and cooking delicious meals. Get started. In this example, we are creating an item using the let keyword of the friendlist array. The first ngFor loops over the groups, each grop contains a country property which we render out on the next line and a people array property.

In this example, we are creating an item using the let keyword of the friendlist array. It will iterate over each item in the array, and will print out the item name and item age, or any other object key we have in the array object. You will see the above output when you save.

The ngFor features are also covered in this video, have a look: What can we do with ngFor? And when the API call finishes, we show the data. I invite you to subscribe to our newsletter to get notified when more posts like this come out:. We can provide our own mechanism for tracking items in a list by using trackBy. But it is static data, so let's change it to dynamic. The use of trackBy it's a performance optimization and is usually not needed by default, it's in principle only needed if running into performance issues. So, we we get 8 items in our list tag. We can see in this example the most common syntax for using ngFor : we are passing to ngFor an iteration expression a loop variable named hero is defined using the keyword let , which is consistent with Javascript syntax the expression is under the form of var i of items , which is consistent with the Javascript of iteration functionality Variable Visibility Note that the loop variable hero is only visible inside the loop, you would not be able to access it outside the ngFor section. Get started. Forum Donate. From a point of view of object identity, the new list contains a whole new set of items, completely different from the previous set. If that happens to be the case, we can configure ngFor to do the tracking by something else other than object identity. Know how to get the index in the array of the item you are looping over. We show some message that the data is loading while the application fetches the data from the API, because it can take some time depending on the server.