How to fix a conditional problem in react

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I am using a condition such that if activeCardId is null nothing returns otherwise it would return something.It is working fine for all values except 0. It is returning nothing when value is 0.

I think it's related to 0 and null.

constructor(props) {
  this.state = {
    activeCardId: null 
  }
}

return(
  {this.state.activeCardId && ( // some random output...)

As this statement means if activecardId is not null then return some random output and return nothing if activecardId is null.

It's because, you are using logical AND (&&).

0 means falsy value, and logical AND dosen't return anything for false values, you should try this

{this.state.activeCardId !==null && ( // some random output...) }

Conditional Rendering – React, a different greeting depending on the value of isLoggedIn prop. There’s more than one way to use conditional expressions in React. And, as with most things in programming, some are better suited than others depending on the problem you’re trying to solve. This tutorial covers the most popular conditional rendering methods:

0 is a falsy value so

this.state.activeCardId

becomes false

7 Ways to Implement Conditional Rendering in React Applications , How do you add if condition in react JS render? Conditional Rendering in React using Ternaries and Logical AND Photo by Brendan Church on Unsplash. There are several ways that your React component can decide what to render. You can use the traditional if statement or the switch statement. In this article, we’ll explore a few alternatives.

this would do the job:

return(
      {this.state.activeCardId!==null && ( // some random output...)

there is difference between null and 0 , 0 is a value, 0 is also falsy in boolean statement while null represents the intentional absence of any object value.

taken from : MDN Null-javascript

What is the difference between render and return in reactjs?, in a method or function is the output of the method or function. Conditional rendering in React using an if statement The most common way of rendering elements conditionally in React is using an if statement: renderDrawer() { if (this.state.expanded) { return (<nav> </nav>); } } In this case, we’re using the if statement within the renderDrawer function.

Check if property exists using React.js, There's more than one way to use conditional expressions in React. An if/else block is the easiest way to solve the problem, but I'm sure you  In this post, i will give you two simple example of how to write if conditional statement in react native app. you can simply use if condition in react js. so let's see bellow example that will help you to understand how it works.

8 conditional rendering methods in React, As a challenge, based on the value of isLoggedIn in our component state, we To solve this, we extract the conditional logic into a function as  7 Ways to Implement Conditional Rendering in React Applications 1. Using an If…else Statement An if…else statement allows us to speficy that a particular action be carried out if a 2. Using Element Variables Element variables are an extension of **Extracting the conditional rendering into a 3.

Conditional rendering in React Native may crash your app , Conditional rendering done wrong leads to errors in React Native that seems Then you see such an error in your logs and scratch your head because It's an easy quick fix that will work and some experiments says that it's  Try it on CodePen. It works because in JavaScript, true && expression always evaluates to expression, and false && expression always evaluates to false. Therefore, if the condition is true, the element right after && will appear in the output. If it is false, React will ignore and skip it.

Comments
  • try this.state.activeCardId !== null ? return something : return null it will work on 0 also as it will check if the value is null or not