Reactjs setState() with a dynamic key name?

问题

EDIT: this is a duplicate, see here

I can\'t find any examples of using a dynamic key name when setting the state. This is what I want to do:

inputChangeHandler : function (event) {
    this.setState( { event.target.id  : event.target.value } );
},

where event.target.id is used as the state key to be updated. Is this not possible in React?

回答1:

Thanks to @Cory's hint, i used this:

inputChangeHandler : function (event) {
    var stateObject = function() {
      returnObj = {};
      returnObj[this.target.id] = this.target.value;
         return returnObj;
    }.bind(event)();

    this.setState( stateObject );    
},

If using ES6 or the Babel transpiler to transform your JSX code, you can accomplish this with computed property names, too:

inputChangeHandler : function (event) {
    this.setState({ [event.target.id]: event.target.value });
    // alternatively using template strings for strings
    // this.setState({ [`key${event.target.id}`]: event.target.value });
}

回答2:

When you need to handle multiple controlled input elements, you can add a name attribute to each element and let the handler function choose what to do based on the value of event.target.name.

For example:

inputChangeHandler(event) {
  this.setState({ [event.target.name]: event.target.value });
}

回答3:

How I accomplished this...

inputChangeHandler: function(event) {
  var key = event.target.id
  var val = event.target.value
  var obj  = {}
  obj[key] = val
  this.setState(obj)
},

回答4:

Just wanted to add, that you can also de-structuring to refactor the code and make it look neater.

inputChangeHandler: function ({ target: { id, value }) {
    this.setState({ [id]: value });
},

回答5:

In loop with .map work like this:

{
    dataForm.map(({ id, placeholder, type }) => {
        return <Input
            value={this.state.type}
            onChangeText={(text) => this.setState({ [type]: text })}
            placeholder={placeholder}
            key={id} />
    })
}

Note the [] in type parameter. Hope this helps :)

回答6:

I had a similar problem.

I wanted to set the state of where the 2nd level key was stored in a variable.

e.g. this.setState({permissions[perm.code]: e.target.checked})

However this isn't valid syntax.

I used the following code to achieve this:

this.setState({
  permissions: {
    ...this.state.permissions,
    [perm.code]: e.target.checked
  }
});

回答7:

With ES6+ you can just do [${variable}]

回答8:

I was looking for a pretty and simple solution and I found this:

this.setState({ [`image${i}`]: image })

Hope this helps

回答9:

Can use a spread syntax, something like this:

inputChangeHandler : function (event) {
    this.setState( { 
        ...this.state,
        [event.target.id]: event.target.value
    } );
},

来源：https://stackoverflow.com/questions/29280445/reactjs-setstate-with-a-dynamic-key-name

标签

javascript

reactjs

computed-properties