React.js setting value of input

Question

I am a beginner with react.js and it's amazing but I am facing a real problem: I need to set the value of an input using plain and pure javascript but for some reason react.js is not working as expected. Take this example: open this URL http://autoescolalatorreta.wix.com/latorreta#!contact/c24vq

You will see there is an "Email" input field which id is "CntctFrm2emailField". I try to change the value of it using javascript with this code:

document.getElementById("CntctFrm2emailField").value = "[email protected]";

But for some reason, React.js is not updating this value on its core cause if you try to send the form (Clicking the SEND button) you will see that it will display an error message saying that the email is not filled right. BUT once I click inside the email field and type any letter and click the SEND button it works fine, I mean, React.js sees the new value.

So how can I change an input value and have React.js to update that value too?

Answer 1

For React 16, use following code. Check this issue.

function setNativeValue(element, value) {
    let lastValue = element.value;
    element.value = value;
    let event = new Event("input", { target: element, bubbles: true });
    // React 15
    event.simulated = true;
    // React 16
    let tracker = element._valueTracker;
    if (tracker) {
        tracker.setValue(lastValue);
    }
    element.dispatchEvent(event);
}

var input = document.getElementById("ID OF ELEMENT");
setNativeValue(input, "VALUE YOU WANT TO SET");

Answer 2

I have written and use this function to trigger the change state for the field:

function doEvent( obj, event ) {
    /* Created by [email protected] */
    var event = new Event( event, {target: obj, bubbles: true} );
    return obj ? obj.dispatchEvent(event) : false;
}

Use it like this:

var el = document.getElementById("CntctFrm2emailField");
el.value = "[email protected]";
doEvent( el, 'input' );

Answer 3

You should post your code in order to get a better/ more to your situation suited answer, but one think that will work is just setting the

defaultValue

instead of value of the input. Take a look at your browsers console, that's what react will log there.

Depending on your code, you can set the states value onKeyUp or similar with a function or fetch the new inputs value when the form is submitted.

Answer 4

I had a form that I needed to submit for some monitoring. I did it like this:

$("input[type=email]").value = "[email protected]"
$("input[type=email]").defaultValue = "[email protected]"
$("input[type=password]").value = "mystellarpassword"
$("input[type=password]").defaultValue = "pinpmystellarpasswordss"
$("input[type=email]").dispatchEvent(new Event('input', {target: $("input[type=email]"), bubbles: true} ));
$("input[type=password]").dispatchEvent(new Event('input', {target: $("input[type=password]"), bubbles: true} ));
$("button.login").click()

Note that for the website I was logging into, I had to set both value and defaultValue. There was some extra validation logic bound to the input.value

Answer 5

First of all, you should never ever work with "document" object in React.js. It is a big no no. You should not access DOM element neither, but if you know what you are doing(like animations) you should create "ref" object, which is off the topic, to access DOM element.

First thing you should have an object inside the state object for your form. Lets say you have "username" and "password" fields in your form.

state={form:{username:"","password:""}

Because input fields have their own state, whatever we type in there will be stored in the input field. We should get rid of the state of input field and only rely on the state object. We want to have single source of truth so convert "input" to “controlled element”. Controlled elements do not have their own state, they get all data, via props and they notify changes to the data by raising events. We are using "value" prop to set inputs value. Since input fields are initialized as empty strings, we will not be able to type something inside input field. Solution is we have to handle the change event for input fields dynamically.

handleChange=e=>{
    const form={...this.state.form}
    form[e.currentTarget.name]=e.currentTarget.value
    this.setState({account})}

<input value={this.state.form.username} change={this.handleChange} name="username"/>
<input value={this.state.form.password} change={this.handleChange} name="password" />