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How to conditional render inside map in a functional component of react js

I have an array. in which i want to iterate over and do conditional checks and display the correct element. i'm using functional component.
Below is an example :
import React, { useState, useEffect } from "react";
function Job(props) {
const [resp_data, setdata] = useState("");
const [look, setlook] = useState("");
useEffect(() => {
// some api calls happen here and response data is stored in state resp_data
}, [props]);
return (
<>
<div className="product_list">
{resp_data.length > 0
? resp_data.map((item) => {
{item.looking_for === "work" ? (
<div className="card-rows work" key={item.id}>
work
</div>
) : (<div className="card-rows no_work" key={item.id}>
No work
</div>)
}
})
: <div>array length is 0</div>}
</div>
</>
);
}
export default Job;
The response data received from api call happening inside useEffect is stored in state variable resp_data.
if resp_data length is not zero, i need to iterate over the list and check if the field value "looking_for" is equal to "work"
if true display a component , else display another component.
if resp_data length is zero display "array length is zero"
this i want to implement, but i could not find many answers for functional components. i have tried many possible ways by switching, changing the braces etc..my hard luck.
Any help is greatly appreciated.

You are not returning anything from the 'map' function.
resp_data.map((item) => (
item.looking_for === "work" ? (
<div className="card-rows work" key={item.id}>
work
</div>
) : (<div className="card-rows no_work" key={item.id}>
No work
</div>)
)
)

setState of child component only when it is called

i have a parent component and i have called the child component in its HTML like this.
render() {
<EditBank
deal={dealDetailData && dealDetailData.id}
open={editBankModalStatus}
headerText={"Edit Bank Account"}
getInvestmentOfferingDetailsById = {() =>this.props.getInvestmentOfferingDetailsById({
id: this.props.match.params.id
})}
bankDetail={bankDetails}
toggleEditModal={() => this.handleEditModal("editBankModalStatus", {})}
/>
}
EditBank component is a modal which is only shown when editBankModalStatus is true and it is set to be true on a button click.
Now i want to set the state of EditBank only when button is clicked and whatever bankDetails has been passed to it.
I have tired componentDidMount lifecycle hook but it updated when component is rendered only.
I want to update the state of EditBank component when it is shown on screen only. Any help is appreciated.

Try do this :
render(){
return (
<div>
{editBankModalStatus === true &&
<EditBank
deal={dealDetailData && dealDetailData.id}
open={editBankModalStatus}
headerText={"Edit Bank Account"}
getInvestmentOfferingDetailsById = {() =>this.props.getInvestmentOfferingDetailsById({
id: this.props.match.params.id
})}
bankDetail={bankDetails}
toggleEditModal={() => this.handleEditModal("editBankModalStatus", {})}
/>
}
</div>
);
}
so EditBank will shown only if editBankModalStatus is true.

How does one pass a prop as null in react?

i have a conundrum.
I have text I want toggling in a component.
basically true => tick and false => untick
but i want a 3rd scenario where I don't want any text displayed
if I don't pass the prop to that component, it is automatically assuming true. can I pass propName={null} or something like that?
or will i have to extract this into a function (i'd much rather not)

If you do not provide the prop to the component it will not be present in the object representing props within that component. You could therefore check whether or not the prop is defined:
const Component = (props) => {
if (props.checked === undefined) {
return <Something />;
}
return <SomethingElse someProp={props.checked} />;
};
Then, this will render Something:
<Component />
And these will all render SomethingElse:
<Component checked />
<Component checked={true} />
<Component checked={false} />

You can have a third state null but then you will need to do explicit comparisons i.e a == false and don't evaluate a as it will become false in case of null as well

Scalable React CSS using 'classnames' with BEM in mind

So, React newbie here... I'll start off by saying I have a simple single page application which consists of a few simple pages.
Using react-router I have a 'top-down' set up for my components. To give you a basic idea of my SPA structure see below:
index -- layout(react routers) --
|--About Page
|--Home Page
|--Contact Page
I am rendering a component called "GlobalHero" from my Home Page component.
Here is the GlobalHero.jsx component.
import React from "react";
var classNames = require('classnames');
import s from '../../../index.scss';
class GlobalHero extends React.Component {
constructor() {
super();
//sets initial state
this.state = {
fadeIn: "",
titleSelected: "",
subTitleSelected: ""
};
}
// <<========= ON COMPONENT RENDER =========
componentDidMount = () => {
console.log("GlobalHero");
console.log(this.props);
this.handleClass("fadeIn");
}
// =========>>
// <<========= CONTROLS THE STATE =========
handleClass = (param) => {
if (param === "fadeIn" && this.state.fadeIn != "true") {
this.setState({fadeIn: "true"});
}
if (param === "titleSelected" && this.state.titleSelected != "true") {
this.setState({titleSelected: "true"});
}
if (param === "subTitleSelected" && this.state.subTitleSelected != "true") {
this.setState({subTitleSelected: "true"});
}
}
// =========>>
render() {
const heroImg = require(`../../../images/hero${this.props.page}.jpg`);
//REMOVES CLASS IN REALTIME BASED ON STATE'S VALUE =========
var containerClasses = classNames({
[s['text-center']]: true,
[s["hidden"]]: this.state.fadeIn != "true",
[s["fadeIn"]]: this.state.fadeIn === "true"
});
var titleClasses = classNames({
[s['blue']]: this.state.titleSelected === "true"
});
var subTitleClasses = classNames({
[s['subTitle']]: true,
[s['text-center']]: true,
[s['blue']]: this.state.subTitleSelected === "true"
});
// =========>>
return (
<div className={s["container-fluid"]}>
<div className={s["row"]}>
<div className={s["col-lg-16"]}>
<div className={containerClasses}>
<img src={heroImg} className={s["hero__img"]}></img>
<h1 onClick={() => this.handleClass("titleSelected")} className={titleClasses}>{this.props.page}!</h1>
<p className={subTitleClasses} onClick={() => this.handleClass("subTitleSelected")}>{this.props.name}, {this.props.age}, {this.props.city}</p>
</div>
</div>
</div>
</div>
);
}
}
export default GlobalHero;
I noticed there is a lot of complexity there for assigning a few simple class names to the component's elements.
I was wondering if there is a better practice for doing this? Maybe
using an external js page to manage my classnames?
Any input or adivce is appreciated... Thankyou in adnvance.

Your title mentions BEM but it looks like you are using CSS Modules, which is inspired by similar ideas but not the same thing.
Anyway, this is quite subjective but I have a few thoughts that are too much to fit in a comment:
Assuming you are using css modules through Webpack's css-loader, you can use camelCase to make your style properties more JS friendly:
loader: "css-loader?modules&camelCase"
Now for .text-center css class name you can simply use s.textCenter instead of s["test-center"].
You could componentize this better: first, you are kind of doing a lot for a single component, but you could break it down into a few smaller components that each have a single responsibility (for example container, title, subtitle). Second, your handleClass() method is doing a lot, when you could just have simple handlers that call setState() without knowing anything about class names. In other words, the component should have props and state, only the render() function deals with how to translate that into class names to render. You also really don't need to check the state's current value before setting it. Just set it to what it should be and let React optimize rendering performance for you.
You have boolean state flags that you store using strings "true" and "false"... this makes it noisy to handle, just store as booleans.
You have a lot of [s["class-name"]]: true which is not necessary; if you always want a class name to be rendered just pass it as an argument to classNames:
classNames(s.subTitle, { [s.blue]: this.state.subTitleSelected })
There's no reason to call a handler on componentDidMount, just initialize the state how you want it.
It looks like you're using bootstrap CSS but not the React Bootstrap components. I would highly recommend using React Bootstrap.
Putting that together I'd have something like:
class GlobalHero extends React.Component {
state = {
fadeIn: true,
titleSelected: false,
subTitleSelected: false
};
handleTitleClick = () => {
this.setState({titleSelected: true});
};
handleSubTitleClick = () => {
this.setState({subTitleSelected: true});
};
render() {
return (
<Grid fluid>
<Row>
<Col lg={16}>
<HeroContainer fadeIn={this.state.fadeIn}>
<HeroImage page={this.props.page} />
<HeroTitle selected={this.state.titleSelected}
onClick={this.handleTitleClick}
page={this.props.page} />
<HeroSubTitle selected={this.state.subTitleSelected}
onClick={this.handleSubTitleClick}
name={this.props.name}
age={this.props.age}
city={this.props.city} />
</HeroContainer>
</Col>
</Row>
</Grid>
);
}
}
const HeroContainer = ({fadeIn, children}) => {
return (
<div className={classNames(s.textCenter, fadeIn ? s.fadeIn : s.hidden)}>
{children}
</div>
);
};
const HeroImage = ({page}) => {
const heroImg = require(`../../../images/hero${page}.jpg`);
return (
<img src={heroImg} className={s.heroImg} />
);
};
const HeroTitle = ({onClick, selected, page}) => (
<h1 onClick={onClick} className={selected ? s.blue : null}>{page}!</h1>
);
const HeroSubTitle = ({onClick, selected, name, age, city}) => (
<p className={classNames(s.subTitle, s.textCenter, { [s.blue]: selected })} onClick={onClick}>
{name}, {age}, {city}
</p>
);
Breaking it into smaller components like this is not completely necessary, but notice how from the perspective of GlobalHero it does nothing with styles, it just sets props and state, and the little parts have no state, they just render the correct styles based on props.
PS maybe this should move to Code Reviews?

Dynamically add React attributes [duplicate]

Is there a way to only add attributes to a React component if a certain condition is met?
I'm supposed to add required and readOnly attributes to form elements based on an Ajax call after render, but I can't see how to solve this since readOnly="false" is not the same as omitting the attribute completely.
The example below should explain what I want, but it doesn't work.
(Parse Error: Unexpected identifier)
function MyInput({isRequired}) {
return <input classname="foo" {isRequired ? "required" : ""} />
}

Apparently, for certain attributes, React is intelligent enough to omit the attribute if the value you pass to it is not truthy. For example:
const InputComponent = function() {
const required = true;
const disabled = false;
return (
<input type="text" disabled={disabled} required={required} />
);
}
will result in:
<input type="text" required>
Update: if anyone is curious as to how/why this happens, you can find details in ReactDOM's source code, specifically at lines 30 and 167 of the DOMProperty.js file.

juandemarco's answer is usually correct, but here is another option.
Build an object how you like:
var inputProps = {
value: 'foo',
onChange: this.handleChange
};
if (condition) {
inputProps.disabled = true;
}
Render with spread, optionally passing other props also.
<input
value="this is overridden by inputProps"
{...inputProps}
onChange={overridesInputProps}
/>

Here is an example of using Bootstrap's Button via React-Bootstrap (version 0.32.4):
var condition = true;
return (
<Button {...(condition ? {bsStyle: 'success'} : {})} />
);
Depending on the condition, either {bsStyle: 'success'} or {} will be returned. The spread operator will then spread the properties of the returned object to Button component. In the falsy case, since no properties exist on the returned object, nothing will be passed to the component.
An alternative way based on Andy Polhill's comment:
var condition = true;
return (
<Button bsStyle={condition ? 'success' : undefined} />
);
The only small difference is that in the second example the inner component <Button/>'s props object will have a key bsStyle with a value of undefined.

Here is an alternative.
var condition = true;
var props = {
value: 'foo',
...(condition && { disabled: true })
};
var component = <div {...props} />;
Or its inline version
var condition = true;
var component = (
<div value="foo" {...(condition && { disabled: true })} />
);

Here's a way I do it.
With a conditional:
<Label
{...{
text: label,
type,
...(tooltip && { tooltip }),
isRequired: required
}}
/>
I still prefer using the regular way of passing props down, because it is more readable (in my opinion) in the case of not have any conditionals.
Without a conditional:
<Label text={label} type={type} tooltip={tooltip} isRequired={required} />

Let’s say we want to add a custom property (using aria-* or data-*) if a condition is true:
{...this.props.isTrue && {'aria-name' : 'something here'}}
Let’s say we want to add a style property if a condition is true:
{...this.props.isTrue && {style : {color: 'red'}}}

You can use the same shortcut, which is used to add/remove (parts of) components ({isVisible && <SomeComponent />}).
class MyComponent extends React.Component {
render() {
return (
<div someAttribute={someCondition && someValue} />
);
}
}

If you use ECMAScript 6, you can simply write like this.
// First, create a wrap object.
const wrap = {
[variableName]: true
}
// Then, use it
<SomeComponent {...{wrap}} />

Using undefined works for most properties:
const name = "someName";
return (
<input name={name ? name : undefined} />
);

This should work, since your state will change after the Ajax call, and the parent component will re-render.
render : function () {
var item;
if (this.state.isRequired) {
item = <MyOwnInput attribute={'whatever'} />
} else {
item = <MyOwnInput />
}
return (
<div>
{item}
</div>
);
}

For some boolean attributes listed by React [1]:
<input disabled={disabled} />
// renders either `<input>` or `<input disabled>`
For other attributes:
<div aria-selected= {selected ? "" : undefined} />
// renders either `<div aria-selected></div>` or `<div></div>`
[1] The list of boolean attributes: https://github.com/facebook/react/blob/3f9480f0f5ceb5a32a3751066f0b8e9eae5f1b10/packages/react-dom/src/shared/DOMProperty.js#L318-L345

For example using property styles for custom container
const DriverSelector = props => {
const Container = props.container;
const otherProps = {
...( props.containerStyles && { style: props.containerStyles } )
};
return (
<Container {...otherProps} >

In React you can conditionally render Components, but also their attributes, like props, className, id, and more.
In React it's very good practice to use the ternary operator which can help you conditionally render Components.
An example also shows how to conditionally render Component and its style attribute.
Here is a simple example:
class App extends React.Component {
state = {
isTrue: true
};
render() {
return (
<div>
{this.state.isTrue ? (
<button style={{ color: this.state.isTrue ? "red" : "blue" }}>
I am rendered if TRUE
</button>
) : (
<button>I am rendered if FALSE</button>
)}
</div>
);
}
}
ReactDOM.render(<App />, document.getElementById("root"));
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react-dom.min.js"></script>
<div id="root"></div>

From my point of view the best way to manage multiple conditional props is the props object approach from #brigand. But it can be improved in order to avoid adding one if block for each conditional prop.
The ifVal helper
rename it as you like (iv, condVal, cv, _, ...)
You can define a helper function to return a value, or another, if a condition is met:
// components-helpers.js
export const ifVal = (cond, trueValue=true, falseValue=null) => {
return cond ? trueValue : falseValue
}
If cond is true (or truthy), the trueValue is returned - or true.
If cond is false (or falsy), the falseValue is returned - or null.
These defaults (true and null) are, usually the right values to allow a prop to be passed or not to a React component. You can think to this function as an "improved React ternary operator". Please improve it if you need more control over the returned values.
Let's use it with many props.
Build the (complex) props object
// your-code.js
import { ifVal } from './components-helpers.js'
// BE SURE to replace all true/false with a real condition in you code
// this is just an example
const inputProps = {
value: 'foo',
enabled: ifVal(true), // true
noProp: ifVal(false), // null - ignored by React
aProp: ifVal(true, 'my value'), // 'my value'
bProp: ifVal(false, 'the true text', 'the false text') // 'my false value',
onAction: ifVal(isGuest, handleGuest, handleUser) // it depends on isGuest value
};
<MyComponent {...inputProps} />
This approach is something similar to the popular way to conditionally manage classes using the classnames utility, but adapted to props.
Why you should use this approach
You'll have a clean and readable syntax, even with many conditional props: every new prop just add a line of code inside the object declaration.
In this way you replace the syntax noise of repeated operators (..., &&, ? :, ...), that can be very annoying when you have many props, with a plain function call.
Our top priority, as developers, is to write the most obvious code that solve a problem.
Too many times we solve problems for our ego, adding complexity where it's not required.
Our code should be straightforward, for us today, for us tomorrow and for our mates.
just because we can do something doesn't mean we should
I hope this late reply will help.

<input checked={true} type="checkbox" />

In react functional component you can try something like this to omit unnecessary tag property.
<div className="something" ref={someCondition ? dummyRef : null} />
This works for me if I need to omit tags like ref, class, etc. But I don't know if that's work for every tag property

<Button {...(isWeb3Enabled ? {} : { isExternal: true })}>
Metamask
</Button>

Given a local variable isRequired You can do the following in your render method (if using a class) or return statement (if using a function component):
<MyComponent required={isRequired ? 'true' : undefined} />
In this case, the attribute will not be added if isRequired is undefined, false, or null (which is different from adding the attribute but setting it to 'false'.) Also note that I am using strings instead of booleans in order to avoid a warning message from react (Boolean value received on non-boolean attribute).

Considering the post JSX In Depth, you can solve your problem this way:
if (isRequired) {
return (
<MyOwnInput name="test" required='required' />
);
}
return (
<MyOwnInput name="test" />
);

I think this may be useful for those who would like attribute's value to be a function:
import { RNCamera } from 'react-native-camera';
[...]
export default class MyView extends React.Component {
_myFunction = (myObject) => {
console.log(myObject.type); //
}
render() {
var scannerProps = Platform.OS === 'ios' ?
{
onBarCodeRead : this._myFunction
}
:
{
// here you can add attribute(s) for other platforms
}
return (
// it is just a part of code for MyView's layout
<RNCamera
ref={ref => { this.camera = ref; }}
style={{ flex: 1, justifyContent: 'flex-end', alignItems: 'center', }}
type={RNCamera.Constants.Type.back}
flashMode={RNCamera.Constants.FlashMode.on}
{...scannerProps}
/>
);
}
}

in an easy way
const InputText= ({required = false , disabled = false, ...props}) =>
(<input type="text" disabled={disabled} required={required} {...props} />);
and use it just like this
<InputText required disabled/>

In addition, you can make other value to Boolean
const MyComponent = function() {
const Required = "yes";
return (
<input
required={Required === "yes"}
type="text"
key={qs.Name}
name="DefaultValue"
label={qs.QuestionTitle}
onChange={(event) => handleInputChange(index, event)}
placeholder={qs.QuestionTitle}
/>
);
}

If it is for a limited number of properties this will do
function MyInput({isRequired}) {
if (isRequired) {
return <input classname="foo" isRequired={isRequired} />
}
return <input classname="foo" />
}
If you have a large number of properties, it will be difficult to write if else conditions for every property and return accordingly. For that, you can push those properties in an object and use the spread operator in the returned element.
function MyInput({ prop1, prop2, ...propN }) {
const props = {};
if (prop1) props.prop1 = prop1;
.
.
.
if (propN) props.propN = propN;
return <input classname="foo" {...props} />
}

You must set as undefined the value for when you do not need the attribute
Example:
<a data-tooltip={sidebarCollapsed?'Show details':undefined}></a>

In React, we pass values to component from parent to child as Props. If the value is false, it will not pass it as props. Also in some situation we can use ternary (conditional operator) also.