I have multiple components in my project, most of which are simple containers for specific content, with a bit of styling. They typically look like this—
function Portion(props) {
return (
<div id={props.id} className={`portion ${props.className}`}>
{props.children}
</div>
)
}
I have the extra ${props.className} so that it’s easy to add more classes if need be. Now, the problem is that if there are no extra classes for that element, React adds an undefined class.
How can I avoid that?
Try using
${props.className || ""}
you can add a condition;
className={`portion ${props.className || ””}`}
Technology :
ReactJS
Todo :
When user chooses a number I need to change just the background
style.
The style is only maintained if this.state.currentPage === number, otherwise it does not show any style although I require the styles changing the background.
Tried Case :
onClick={this.handleClick} style={this.state.currentPage === number ?
styles.paginationButtons : [styles.paginationButtons,
{backgroundColor:'blue'}]}>
Try updating your code so that you supply the dynamic styles to your component without the use of arrays.
You should be able to do so in this way:
style={ (this.state.currentPage === number ? styles.paginationButtons : { backgroundColor:'blue', ...styles.paginationButtons }) }
I'm doing some React right now and I was wondering if there is a "correct" way to do conditional styling. In the tutorial they use
style={{
textDecoration: completed ? 'line-through' : 'none'
}}
I prefer not to use inline styling so I want to instead use a class to control conditional styling. How would one approach this in the React way of thinking? Or should I just use this inline styling way?
<div style={{ visibility: this.state.driverDetails.firstName != undefined? 'visible': 'hidden'}}></div>
Checkout the above code. That will do the trick.
If you prefer to use a class name, by all means use a class name.
className={completed ? 'text-strike' : null}
You may also find the classnames package helpful. With it, your code would look like this:
className={classNames({ 'text-strike': completed })}
There's no "correct" way to do conditional styling. Do whatever works best for you. For myself, I prefer to avoid inline styling and use classes in the manner just described.
POSTSCRIPT [06-AUG-2019]
Whilst it remains true that React is unopinionated about styling, these days I would recommend a CSS-in-JS solution; namely styled components or emotion. If you're new to React, stick to CSS classes or inline styles to begin with. But once you're comfortable with React I recommend adopting one of these libraries. I use them in every project.
If you need to conditionally apply inline styles (apply all or nothing) then this notation also works:
style={ someCondition ? { textAlign:'center', paddingTop: '50%'} : {}}
In case 'someCondition' not fulfilled then you pass empty object.
instead of this:
style={{
textDecoration: completed ? 'line-through' : 'none'
}}
you could try the following using short circuiting:
style={{
textDecoration: completed && 'line-through'
}}
https://codeburst.io/javascript-short-circuit-conditionals-bbc13ac3e9eb
key bit of information from the link:
Short circuiting means that in JavaScript when we are evaluating an AND expression (&&), if the first operand is false, JavaScript will short-circuit and not even look at the second operand.
It's worth noting that this would return false if the first operand is false, so might have to consider how this would affect your style.
The other solutions might be more best practice, but thought it would be worth sharing.
inline style handling
style={{backgroundColor: selected ? 'red':'green'}}
using Css
in js
className={`section ${selected && 'section_selected'}`}
in css
.section {
display: flex;
align-items: center;
}
.section_selected{
background-color: whitesmoke;
border-width: 3px !important;
}
same can be done with Js stylesheets
Another way, using inline style and the spread operator
style={{
...completed ? { textDecoration: completed } : {}
}}
That way be useful in some situations where you want to add a bunch of properties at the same time base on the condition.
First, I agree with you as a matter of style - I would also (and do also) conditionally apply classes rather than inline styles. But you can use the same technique:
<div className={{completed ? "completed" : ""}}></div>
For more complex sets of state, accumulate an array of classes and apply them:
var classes = [];
if (completed) classes.push("completed");
if (foo) classes.push("foo");
if (someComplicatedCondition) classes.push("bar");
return <div className={{classes.join(" ")}}></div>;
If you want assign styles based on condition, its better you use a class name for styles. For this assignment, there are different ways. These are two of them.
1.
<div className={`another-class ${condition ? 'active' : ''}`} />
<div className={`another-class ${condition && 'active'}`} />
style={{
whiteSpace: "unset",
wordBreak: "break-all",
backgroundColor: one.read == false && "#e1f4f3",
borderBottom:'0.8px solid #fefefe'
}}
I came across this question while trying to answer the same question. McCrohan's approach with the classes array & join is solid.
Through my experience, I have been working with a lot of legacy ruby code that is being converted to React and as we build the component(s) up I find myself reaching out for both existing css classes and inline styles.
example snippet inside a component:
// if failed, progress bar is red, otherwise green
<div
className={`progress-bar ${failed ? 'failed' : ''}`}
style={{ width: this.getPercentage() }}
/>
Again, I find myself reaching out to legacy css code, "packaging" it with the component and moving on.
So, I really feel that it is a bit in the air as to what is "best" as that label will vary greatly depending on your project.
Sorted way to apply inline styling on some condition.
style={areFieldsDisabled ? {opacity: 0.5} : '' }
If you do not want to overwrite the initial style, you can use empty styling with {}. For instance, assigning a background-color, when you need to keep the initial color if the condition is not met.
style={ onError ? {backgroundColor: 'red'} : {} }
style={ completed ? {textDecoration: 'line-through'} : {} }
The best way to handle styling is by using classes with set of css properties.
example:
<Component className={this.getColor()} />
getColor() {
let class = "badge m2";
class += this.state.count===0 ? "warning" : danger;
return class;
}
You can use somthing like this.
render () {
var btnClass = 'btn';
if (this.state.isPressed) btnClass += ' btn-pressed';
else if (this.state.isHovered) btnClass += ' btn-over';
return <button className={btnClass}>{this.props.label}</button>;
}
Or else, you can use classnames NPM package to make dynamic and conditional className props simpler to work with (especially more so than conditional string manipulation).
classNames('foo', 'bar'); // => 'foo bar'
classNames('foo', { bar: true }); // => 'foo bar'
classNames({ 'foo-bar': true }); // => 'foo-bar'
classNames({ 'foo-bar': false }); // => ''
classNames({ foo: true }, { bar: true }); // => 'foo bar'
classNames({ foo: true, bar: true }); // => 'foo bar'
In case someone uses Typescript (which does not except null values for style) and wants to use react styling, I would suggest this hack:
<p
style={choiceStyle ? styles.choiceIsMade : styles.none}>
{question}
</p>
const styles = {
choiceIsMade: {...},
none: {}
}
Change Inline CSS Conditionally Based on Component State.
This is also the Correct way to handle conditional styling in React.
condition ? expressionIfTrue : expressionIfFalse;
example =>
{this.state.input.length > 15 ? inputStyle={border: '3px solid red'}: inputStyle }
This code means that if the character is more than 15 entered in the input field, then our input field's border will be red and the length of the border will be 3px.
I have the following HTML element with AngularJS directives:
<div class="progress">
<span ng-repeat="timeRangeObject in timeRangeObjects" style="width: {{timeRangeObject.percentage}}%" ng-class="vm.showVacation == true ? 'progress-bar timerange-{{timeRangeObject.containerType}}' : 'progress-bar timerange-PADDING'" />
</div>
So I concat more than one progress bar with different types/colors.
With the checkbox I will set specific progress bars to color transparent.
Therefore I would need something like this:
... ng-class="vm.showVacation == true ? 'progress-bar timerange-{{timeRangeObject.containerType}}' : 'progress-bar timerange-PADDING | timeRangeObject.containerType == 'XY''"
-> so I would need a filter concerning the ng-class else statement.
Is this possible? The important thing is that only color should change but progress bar should stay where it is.
Thanks a lot
[EDIT]
Here is a link to my problem:
My Example
You have a done a lot of thing that is better if you correct first of all don't use style="width:{{}}" is better if you use ng-style so you don't have to use the bracket, and to answer to your question you can write like this in your ng-class:
<div ng-class="foo()">
js
$scope.foo=function(){
return /*here you put your condition sorry but i didn't understand
the conditions you need*/
}
you can do this with your style attribute too.
Could somebody please tell me where this is going wrong? I basically have a simple check of a value - if the value is true, it should set the class to headerOn. If false, it should be headerOff. Easy. Here's the code:
<div ng-class="headerCheck ? 'headerOn' : 'headerOff'">
And the function that I hit:
$scope.headerControl = function() {
$scope.headerCheck = true;
console.log($scope.headerCheck);
}
I can confirm that the log is true. Any ideas why this isn't working for me?
The problem is the syntax here.
The correct approach would be these:
<div class="{{headerCheck ? 'headerOn' : 'headerOff'}}">
or
<div ng-class="{'headerOn': headerCheck, 'headerOff' : !headerCheck }">
The syntax for ng-class is wrong, it should be:
ng-class="{'headerOn' : headerCheck, 'headerOff' : !headerCheck}"
What you have is correct, but you are not telling angularjs that it needs to evaluate what is in the "" as an angular expression. As Karthik stated, you could change the div to
<div ng-class="{headerCheck ? 'headerOn' : 'headerOff'}">
which then makes headerCheck ? 'headerOn' : 'headerOff' an angularjs expression.
EDIT:
Since you did not give a chunk of your code and only gave you snippet, you may want to make sure that the div you referenced in your question is being controlled by the same controller that has your $scope.headerControl function included in.