to call onChange event after pressing Enter key

Question

I am new to Bootstrap and stuck with this problem. I have an input field and as soon as I enter just one digit, the function from onChange is called, but I want

Answer 1

According to React Doc, you could listen to keyboard events, like onKeyPress or onKeyUp, not onChange.

var Input = React.createClass({
  render: function () {
    return <input type="text" onKeyDown={this._handleKeyDown} />;
  },
  _handleKeyDown: function(e) {
    if (e.key === 'Enter') {
      console.log('do validate');
    }
  }
});

Update: Use React.Component

Here is the code using React.Component which does the same thing

class Input extends React.Component {
  _handleKeyDown = (e) => {
    if (e.key === 'Enter') {
      console.log('do validate');
    }
  }

  render() {
    return <input type="text" onKeyDown={this._handleKeyDown} />
  }
}

Here is the jsfiddle.

Update 2: Use a functional component

const Input = () => {
  const handleKeyDown = (event) => {
    if (event.key === 'Enter') {
      console.log('do validate')
    }
  }

  return <input type="text" onKeyDown={handleKeyDown} />
}

Answer 2

React users, here's an answer for completeness.

React version 16.4.2

You either want to update for every keystroke, or get the value only at submit. Adding the key events to the component works, but there are alternatives as recommended in the official docs.

Controlled vs Uncontrolled components

Controlled

From the Docs - Forms and Controlled components:

In HTML, form elements such as input, textarea, and select typically maintain their own state and update it based on user input. In React, mutable state is typically kept in the state property of components, and only updated with setState().

We can combine the two by making the React state be the “single source of truth”. Then the React component that renders a form also controls what happens in that form on subsequent user input. An input form element whose value is controlled by React in this way is called a “controlled component”.

If you use a controlled component you will have to keep the state updated for every change to the value. For this to happen, you bind an event handler to the component. In the docs' examples, usually the onChange event.

Example:

1) Bind event handler in constructor (value kept in state)

constructor(props) {
    super(props);
    this.state = {value: ''};

    this.handleChange = this.handleChange.bind(this);
}

2) Create handler function

handleChange(event) {
    this.setState({value: event.target.value});
}

3) Create form submit function (value is taken from the state)

handleSubmit(event) {
    alert('A name was submitted: ' + this.state.value);
    event.preventDefault();
}

4) Render

<form onSubmit={this.handleSubmit}>
    <label>
      Name:
      <input type="text" value={this.state.value} onChange={this.handleChange} />
    </label>
    <input type="submit" value="Submit" />
</form>

If you use controlled components, your handleChange function will always be fired, in order to update and keep the proper state. The state will always have the updated value, and when the form is submitted, the value will be taken from the state. This might be a con if your form is very long, because you will have to create a function for every component, or write a simple one that handles every component's change of value.

Uncontrolled

From the Docs - Uncontrolled component

In most cases, we recommend using controlled components to implement forms. In a controlled component, form data is handled by a React component. The alternative is uncontrolled components, where form data is handled by the DOM itself.

To write an uncontrolled component, instead of writing an event handler for every state update, you can use a ref to get form values from the DOM.

The main difference here is that you don't use the onChange function, but rather the onSubmit of the form to get the values, and validate if neccessary.

Example:

1) Bind event handler and create ref to input in constructor (no value kept in state)

constructor(props) {
    super(props);
    this.handleSubmit = this.handleSubmit.bind(this);
    this.input = React.createRef();
}

2) Create form submit function (value is taken from the DOM component)

handleSubmit(event) {
    alert('A name was submitted: ' + this.input.current.value);
    event.preventDefault();
}

3) Render

<form onSubmit={this.handleSubmit}>
    <label>
      Name:
      <input type="text" ref={this.input} />
    </label>
    <input type="submit" value="Submit" />
</form>

If you use uncontrolled components, there is no need to bind a handleChange function. When the form is submitted, the value will be taken from the DOM and the neccessary validations can happen at this point. No need to create any handler functions for any of the input components as well.

Your issue

Now, for your issue:

... I want it to be called when I push 'Enter when the whole number has been entered

If you want to achieve this, use an uncontrolled component. Don't create the onChange handlers if it is not necessary. The enter key will submit the form and the handleSubmit function will be fired.

Changes you need to do:

Remove the onChange call in your element

var inputProcent = React.CreateElement(bootstrap.Input, {type: "text",
    //    bsStyle: this.validationInputFactor(),
    placeholder: this.initialFactor,
    className: "input-block-level",
    // onChange: this.handleInput,
    block: true,
    addonBefore: '%',
    ref:'input',
    hasFeedback: true
});

Handle the form submit and validate your input. You need to get the value from your element in the form submit function and then validate. Make sure you create the reference to your element in the constructor.

  handleSubmit(event) {
      // Get value of input field
      let value = this.input.current.value;
      event.preventDefault();
      // Validate 'value' and submit using your own api or something
  }

Example use of an uncontrolled component:

class NameForm extends React.Component {
  constructor(props) {
    super(props);
    // bind submit function
    this.handleSubmit = this.handleSubmit.bind(this);
    // create reference to input field
    this.input = React.createRef();
  }

  handleSubmit(event) {
    // Get value of input field
    let value = this.input.current.value;
    console.log('value in input field: ' + value );
    event.preventDefault();
    // Validate 'value' and submit using your own api or something
  }

  render() {
    return (
      <form onSubmit={this.handleSubmit}>
        <label>
          Name:
          <input type="text" ref={this.input} />
        </label>
        <input type="submit" value="Submit" />
      </form>
    );
  }
}

ReactDOM.render(
  <NameForm />,
  document.getElementById('root')
);

Answer 3

pressing Enter when the focus in on a form control (input) normally triggers a submit (onSubmit) event on the form itself (not the input) so you could bind your this.handleInput to the form onSubmit.

Alternatively you could bind it to the blur (onBlur) event on the input which happens when the focus is removed (e.g. tabbing to the next element that can get focus)

Answer 4

You can also write a little wrapper function like this

const onEnter = (event, callback) => event.key === 'Enter' && callback()

Then consume it on your inputs

<input 
    type="text" 
    placeholder="Title of todo" 
    onChange={e => setName(e.target.value)}
    onKeyPress={e => onEnter(e, addItem)}/>

Answer 5

You can use event.key

function Input({onKeyPress}) {
  return (
    <div>
      <h2>Input</h2>
      <input type="text" onKeyPress={onKeyPress}/>
    </div>
  )
}

class Form extends React.Component {
  state = {value:""}

  handleKeyPress = (e) => {
    if (e.key === 'Enter') {
      this.setState({value:e.target.value})
    }
  }

  render() {
    return (
      <section>
        <Input onKeyPress={this.handleKeyPress}/>
        <br/>
        <output>{this.state.value}</output>
      </section>
    );
  }
}

ReactDOM.render(
  <Form />,
  document.getElementById("react")
)

<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.6.3/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.6.3/umd/react-dom.production.min.js"></script>
<div id="react"></div>

Answer 6

You can use onKeyPress directly on input field. onChange function changes state value on every input field change and after Enter is pressed it will call a function search().

<input
    type="text"
    placeholder="Search..."
    onChange={event => {this.setState({query: event.target.value})}}
    onKeyPress={event => {
                if (event.key === 'Enter') {
                  this.search()
                }
              }}
/>