Ng if

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In this post, we are going to cover all the features that we have available for using the Angular ngIf core directive. Besides the most commonly used features, we are going to learn how to avoid a potential ngIf anti-pattern that we might run into while developing more complex UI screens that consume a lot of Observable data coming from different sources backend, Observable services, stores, etc. This post is part of our ongoing series on Angular Core features, you can find all the articles available here. So without further ado, let's get started learning everything that we need to know about Angular ngIf! Note: If instead of ngIf you are looking for the if syntax, then check my other guide instead: Angular if: Complete Guide. Even though HTML is also a programming language in its own right, it does not have an if statement, unlike for example Javascript. The Angular ngIf directive works essentially as an if statement for HTML, adding this missing feature to the language under the form of the special ngIf attribute.

Ng if

W3Schools offers a wide range of services and products for beginners and professionals, helping millions of people everyday to learn and master new skills. Create your own website with W3Schools Spaces - no setup required. Host your own website, and share it to the world with W3Schools Spaces. Build fast and responsive sites using our free W3. CSS framework. W3Schools Coding Game! Help the lynx collect pine cones. The ng-if directive removes the HTML element if the expression evaluates to false. The ng-if directive is different from the ng-hide, which hides the display of the element, where the ng-if directive completely removes the element from the DOM. If you want to report an error, or if you want to make a suggestion, do not hesitate to send us an e-mail:. Search field. My W3Schools Tutorials.

If you wish to change this at any time you may do so by clicking here. Nice and simple! You can name template variables as you wish, ng if.

See the bundle then add to cart and your discount is applied. Follow the ultimate Angular roadmap. The most complete guide to learning Angular ever built. Trusted by 82, students. Google Developer Expert. NgIf allows us to show and hide content based on the state of a piece of data.

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.

Ng if

Also, we will find out how the ngIf directive differs from using the "hidden" attribute. When we got the basics, we will move on to more advanced topics like using the "else"-condition with ng-template and logical operators. Finally, we will take a look under the hood and see, how angular actually uses the ngIf directive. Also, this condition does also apply to all child elements of the element that has the ngIf directive:.

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The ngIf directive can take as input any valid Typescript expression and not just a boolean. So how can we improve on this, is there an alternative way? AngularJS ng-change Directive. Angular forms FormControlName Directive. If the screen is going to be complex and accept multiple observables, we might as well use it from the beginning. Conclusion You have gone through the Angular ngIf directive and how it is used to make handling comparisons easy. W3schools Pathfinder. The example given with combineLatest is a common one, but feel free to add any other combination of operators in order to get exactly the data observable that the view needs. Create your own website with W3Schools Spaces - no setup required. Open up your ng canvas project you already unzipped in VS Code, and inside your src directory you will find an app folder. The Single Data Observable pattern For simpler screens, the issues that we have discussed above are probably not a huge problem. While using W3Schools, you agree to have read and accepted our terms of use , cookie and privacy policy.

W3Schools offers a wide range of services and products for beginners and professionals, helping millions of people everyday to learn and master new skills.

If we could use an "if" syntax in HTML, we will also need an else clause, just like in Javascript we have the if-else statement. What we are talking about here, is the repeated use of this ngIf and async pipe combination, just for the purpose of accessing data, and nothing more. The ngIf directive can take as input any valid Typescript expression and not just a boolean. Conclusion You have gone through the Angular ngIf directive and how it is used to make handling comparisons easy. Just like most programming languages, Angular has directives like if , for and switch for handling comparisons. Either one of the two templates coursesList or noCourses is going to be instantiated, depending on the truthiness of the courses. Thinking more about our JavaScript, this syntax aligns more with thinking in the flow of ternary statements. Here are a few examples of what would happen if we passed other primitive types to ngIf : And here are some more examples of passing arrays and objects to ngIf : As we can see, all that it matters to determine if an element is shown or not is the truthiness of the expression passed to ngIf. Besides avoiding the unnecessary nesting and making the template much easier to read and reason about, this pattern also helps with the UI issues that we mentioned before. In general, while building Angular applications, we should always prefer to hide elements using ngIf instead of using plain CSS. Related Articles. Besides booleans we can also pass to ngIf for example strings, arrays, objects, etc. This will show or hide the content of ng-container , without having to create an extra div just for that: How does ngIf compare to hiding elements using CSS? Modify your your comparisons. You might have come across some components with templates that look a lot like this: This page is made up of three different peer sections, at the same level of the HTML tree: the header only needs the user the body needs all data: courses, the lessons, and the user the footer only needs the courses and the lessons In order to consume the Observable data, we had to resort to repeating the use of ngIf and the async pipe, at multiple levels of the page.