Let’s consider an example and bind classes in it. When an object moves around the screen, slides, or fades, we expect that object to be consistent and easy to track as it conveys the information it’s trying to show us. Want to learn more about creating great web apps? We have used three modifiers in the example - trim, number, and lazy. Try adding an index to the v-for loop and setting it as the value for the :key, as some people do to “satisfy” the condition and remove the warning. For that we’ll need a custom navigation guard for the router in main.js. When :key is missing, Vue will use internal functions or algorithms to try to figure out the best way to avoid moving DOM elements around. Progress collects the Personal Information set out in our Privacy Policy and Privacy Policy for California Residents and uses it for the purposes stated in that policy. When this animation is not consistent or clear, it creates a bad user experience and also causes problems tracking the information. So you find yourself writing a Vue app. We have two lists of items been fed by the same pool of data, a property called list. As we can see above, both classes get applied to the div. The key property will assist Vue in making a better job of recognizing each element on the list, and not destroying elements potentially that could hold elements with a state within them. Now that you understand exactly what it is trying to accomplish, and the reasons behind the “magic”, you can make better calls when developing your loops - and obtain more granular control over your application and how it performs. Working on improving health and education, reducing inequality, and spurring economic growth? Problem I read the news about prettier supporting vue files. You’ll probably have to stick with manually updating document.title for such use-cases. But often times you’ll want the title of the browser to change when the page changes, right? There is a class defined in the style .active with the background color as red. Hooray. After logging in you can close it and return to this page. The first clickme shows the href as hreflink, and the second one shows it in {{hreflink}}, while the last one displays the correct url as we require. Another example is the v-on directive, which listens to DOM events: Here the argument is the event name to listen to. Join free newsletter and never miss out on new tips, tutorials, and more. This is useful when you are using Vue.js to apply dynamic behavior to some existing markup, but can feel verbose for some frequently used directives. If for some unknown reason to the user, the object magically disappeared, and then another one slid to the left, it would create confusion and the animation - rather than serving a strong visual cue - would create discomfort and confusion. At the same time, the need for the v- prefix becomes less important when you are building a SPA, where Vue manages every template. In this example we simply add a title attribute text to the title tag of a button with v-bind. For example, the .prevent modifier tells the v-on directive to call event.preventDefault() on the triggered event: You’ll see other examples of modifiers later, for v-on and for v-model, when we explore those features. You get paid, we donate to tech non-profits. Both lists are wrapped inside a component that will allow us to visually identify what is happening. The contents of the span will be replaced with the value of the rawHtml property, interpreted as plain HTML - data bindings are ignored. Elements like ,