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How to pass arguments to functions in React js?

Tags:

reactjs

  1. I want to display person's email in the alert window. But, I do not know how to pass email as arguments to displayAlert method. Also, it wont let me use either. So, I have to assign displayAlert methos to a variable and use it in onClick. I do not know why it wont let me call it directly.

    class People extends React.Component{
    render (){
            var handleClick = this.displayAlert;
            var items = this.props.items.map(function(item) {
                return(
                    <ul key = {item.id}>
                        <li>
                            <button onClick= {handleClick}>{item.lastName + ', ' + item.firstName}</button>
                        </li>
                    </ul>
                )
            });
            return (<div>{items}</div>);
     }
    
    displayAlert (){
        alert('Hi');
    }
    }
    
     class PersonList extends React.Component{
         render () {
            return (
        <div>
            <People items={this.props.people}/> /* People is an array of people*/
        </div>
        );
      }
    }
    
like image 495
user3528213 Avatar asked Jun 02 '15 23:06

user3528213


2 Answers

The ES6 way:

Using arrow functions =>

const items = this.props.items.map((item) => (
  <ul key={item.id}>
    <li>
      <button onClick={() => this.displayAlert(item.email)}>
        {item.lastName + ', ' + item.firstName}
      </button>
    </li>
  </ul>
));

onClick the anonymous function is called and executes this.displayAlert(item.email)

The ES5 way:

You could do this using .bind and passing the parameter in there.

You should also pass this or use bind to keep the proper context on your .map function:

var items = this.props.items.map(function(item) {
  return (
    <ul key={item.id}>
      <li>
        <button onClick={this.displayAlert.bind(this, item.email)}>
          {item.lastName + ', ' + item.firstName}
        </button>
      </li>
    </ul>
  );
}, this);

Shown in the example here: React - Communicate Between Components

like image 69
Austin Greco Avatar answered Oct 16 '22 01:10

Austin Greco


Using arrow function and babel plugin "transform-class-properties"

class People extends React.Component {
  render() {
    return (
      <ul>
        { this.props.items.map( (item) => (
          <li key={item.id}>
            <button onClick={this.displayAlert(item)}>
              {item.lastName + ', ' + item.firstName}
            </button>
          </li>
        ))}
      </ul>
    )
  }

  displayAlert = (item) => (event) => {
    // you can access the item object and the event object
    alert('Hi');
  }
}
like image 36
miguel savignano Avatar answered Oct 16 '22 01:10

miguel savignano