Javascript – Formik component changing an uncontrolled input of type text to be controlled

formikformsjavascriptreactjs

I am using Formik with an array, where the items are being passed from a parent and retrieved like this:

updateState (){
    this.state.choices = this.props.choices
    this.state.questionId = this.props.questionId
  }
  render() {
    this.updateState()
    var choices = this.state.choices
    console.log(choices)
    return ( ...

I am originally initializing the values as empty or 0:

  constructor(props){
    super(props);
    this.state = {
      choices : [],
      questionId: 0
    };
  }

While this seems like it should work, I am getting the error that a component is changing an uncontrolled input of type text to be controlled. understand this is due to my use of this.state but I'm unsure how to actually fix this.

What I have done so far, since I am using Formik, is change my export to look like this:

  export default withFormik({
  mapPropsToValues: (props) => ({
    choices: [{
    id: '',
    value: '',
    weight: '',
    impact: ''}]
  }),
})(Choices)

It's unclear if I should be mapping props at all, or if I should be using something more like:

export default withFormik({
  mapPropsToValues: (props) => ({

    id: '',
    value: '',
    weight: '',
    impact: ''
  }),
})(Choices)

All I know is that I am unable to click to push a new object onto the array that I am working with, so the functionality is basically frozen until I can figure out the state of the un/controlled input element.

Any idea where I am going wrong?

Best Answer

Fixing the HTML and the {choices[index].id} bits cleared this error.

E.g.:

<div className="col">
                        <label htmlFor={choices[index].id}>{choices[index].id}</label>
                        <Field name={choices[index].id} placeholder={choices[index].value} type="text"/>
                        <ErrorMessage name={choices[index].id} component="div" className="field-error" />
                      </div>

JavaScript

Try it yourself on JSFiddle.

You can filter the input values of a text <input> with the following setInputFilter function (supports Copy+Paste, Drag+Drop, keyboard shortcuts, context menu operations, non-typeable keys, the caret position, different keyboard layouts, and all browsers since IE 9):

// Restricts input for the given textbox to the given inputFilter function.
function setInputFilter(textbox, inputFilter) {
  ["input", "keydown", "keyup", "mousedown", "mouseup", "select", "contextmenu", "drop"].forEach(function(event) {
    textbox.addEventListener(event, function() {
      if (inputFilter(this.value)) {
        this.oldValue = this.value;
        this.oldSelectionStart = this.selectionStart;
        this.oldSelectionEnd = this.selectionEnd;
      } else if (this.hasOwnProperty("oldValue")) {
        this.value = this.oldValue;
        this.setSelectionRange(this.oldSelectionStart, this.oldSelectionEnd);
      } else {
        this.value = "";
      }
    });
  });
}

You can now use the setInputFilter function to install an input filter:

setInputFilter(document.getElementById("myTextBox"), function(value) {
  return /^\d*\.?\d*$/.test(value); // Allow digits and '.' only, using a RegExp
});

See the JSFiddle demo for more input filter examples. Also note that you still must do server side validation!

TypeScript

Here is a TypeScript version of this.

function setInputFilter(textbox: Element, inputFilter: (value: string) => boolean): void {
    ["input", "keydown", "keyup", "mousedown", "mouseup", "select", "contextmenu", "drop"].forEach(function(event) {
        textbox.addEventListener(event, function(this: (HTMLInputElement | HTMLTextAreaElement) & {oldValue: string; oldSelectionStart: number | null, oldSelectionEnd: number | null}) {
            if (inputFilter(this.value)) {
                this.oldValue = this.value;
                this.oldSelectionStart = this.selectionStart;
                this.oldSelectionEnd = this.selectionEnd;
            } else if (Object.prototype.hasOwnProperty.call(this, 'oldValue')) {
                this.value = this.oldValue;
                if (this.oldSelectionStart !== null &&
                    this.oldSelectionEnd !== null) {
                    this.setSelectionRange(this.oldSelectionStart, this.oldSelectionEnd);
                }
            } else {
                this.value = "";
            }
        });
    });
}

jQuery

There is also a jQuery version of this. See this answer.

HTML 5

HTML 5 has a native solution with <input type="number"> (see the specification), but note that browser support varies:

Most browsers will only validate the input when submitting the form, and not when typing.
Most mobile browsers don't support the step, min and max attributes.
Chrome (version 71.0.3578.98) still allows the user to enter the characters e and E into the field. Also see this question.
Firefox (version 64.0) and Edge (EdgeHTML version 17.17134) still allow the user to enter any text into the field.

Try it yourself on w3schools.com.

Javascript – Best way to track onchange as-you-type in input type=”text”

These days listen for oninput. It feels like onchange without the need to lose focus on the element. It is HTML5.

It’s supported by everyone (even mobile), except IE8 and below. For IE add onpropertychange. I use it like this:

const source = document.getElementById('source');
const result = document.getElementById('result');

const inputHandler = function(e) {
  result.innerHTML = e.target.value;
}

source.addEventListener('input', inputHandler);
source.addEventListener('propertychange', inputHandler); // for IE8
// Firefox/Edge18-/IE9+ don’t fire on <select><option>
// source.addEventListener('change', inputHandler);

<input id="source">
<div id="result"></div>

Best Answer

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Javascript – Best way to track onchange as-you-type in input type=”text”

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