How do I create a dynamic drop down list with reac

问题:

The example code in the react-bootstrap site shows the following. I need to drive the options using an array, but I'm having trouble finding examples that will compile.

<Input type="select" label="Multiple Select" multiple>
  <option value="select">select (multiple)</option>
  <option value="other">...</option>
</Input>

回答1:

You can start with these two functions. The first will create your select options dynamically based on the props passed to the page. If they are mapped to the state then the select will recreate itself.

 createSelectItems() {
     let items = [];         
     for (let i = 0; i <= this.props.maxValue; i++) {             
          items.push(<option key={i} value={i}>{i}</option>);   
          //here I will be creating my options dynamically based on
          //what props are currently passed to the parent component
     }
     return items;
 }  

onDropdownSelected(e) {
    console.log("THE VAL", e.target.value);
    //here you will see the current selected value of the select input
}

Then you will have this block of code inside render. You will pass a function reference to the onChange prop and everytime onChange is called the selected object will bind with that function automatically. And instead of manually writing your options you will just call the createSelectItems() function which will build and return your options based on some constraints (which can change).

  <Input type="select" onChange={this.onDropdownSelected} label="Multiple Select" multiple>
       {this.createSelectItems()}
  </Input>

回答2:

My working example

this.countryData = [
    { value: 'USA', name: 'USA' },
    { value: 'CANADA', name: 'CANADA' }            
];

<select name="country" value={this.state.data.country}>
    {this.countryData.map((e, key) => {
        return <option key={key} value={e.value}>{e.name}</option>;
    })}
</select>

回答3:

A 1 liner would be:

import * as YourTypes from 'Constants/YourTypes';
....
<Input ...>
    {Object.keys(YourTypes).map((t,i) => <option key={i} value={t}>{t}</option>)}
</Input>

Assuming you store the list constants in a separate file (and you should, unless they're downloaded from a web service):

# YourTypes.js
export const MY_TYPE_1="My Type 1"
....

回答4:

You need to add key for mapping otherwise it throws warning because each props should have a unique key.Code revised below: let optionTemplate = this.state.values.map((v, index) => ({v.name}));

回答5:

You can create dynamic select options by map()

Example code

return (
    <select className="form-control"
            value={this.state.value}
            onChange={event => this.setState({selectedMsgTemplate: event.target.value})}>
        {
            templates.map(msgTemplate => {
                return (
                    <option key={msgTemplate.id} value={msgTemplate.text}>
                        Select one...
                    </option>
                )
            })
        }
    </select>
)
  </label>
);

回答6:

// on component load, load this list of values
// or we can get this details from api call also    
const animalsList = [
{
    id: 1,
    value: 'Tiger'
}, {
    id: 2,
    value: 'Lion'
}, {
    id: 3,
    value: 'Dog'
}, {
    id: 4,
    value: 'Cat'
}
];

// generage select dropdown option list dynamically
function Options({ options }) {
    return (
        options.map(option => 
                    <option key={option.id} value={option.value}>                                   
                    {option.value}
                    </option>)
                   );
}

<select
name="animal"
className="form-control">
<Options options={animalsList} />
</select>

回答7:

bind dynamic drop using arrow function.

class BindDropDown extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      values: [
        { name: 'One', id: 1 },
        { name: 'Two', id: 2 },
        { name: 'Three', id: 3 },
        { name: 'four', id: 4 }
      ]
    };
  }
  render() {
    let optionTemplate = this.state.values.map(v => (
      <option value={v.id}>{v.name}</option>
    ));

    return (
      <label>
        Pick your favorite Number:
        <select value={this.state.value} onChange={this.handleChange}>
          {optionTemplate}
        </select>
      </label>
    );
  }
}

ReactDOM.render(
  <BindDropDown />,
  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">
    <!-- This element's contents will be replaced with your component. -->
</div>