I've been trying to write a bot to autoplete some forms on a website, by copy+pasting the script into the Chrome console. (Nothing illegal.) However, the problem is that this website is written in React, which means that the controlled ponents they use for forms interfere with simple form.value changes. If I try to fill a form using something akin to form.value = answer, I still need to do a manual keypress on the form to have it work, which isn't suited for my needs of automation.

What I have tried so far:
- Filling in the form.value and firing a keypress/keydown/keyup afterwards.
- Filling in the form.value minus one letter and firing a keypress afterwards, corresponding to the letter that was missed out.

For some strange reason afterwards, as well, the enter key doesn't work to submit until I do the manual keypress.

Can anyone help me out? Thanks!

I've been trying to write a bot to autoplete some forms on a website, by copy+pasting the script into the Chrome console. (Nothing illegal.) However, the problem is that this website is written in React, which means that the controlled ponents they use for forms interfere with simple form.value changes. If I try to fill a form using something akin to form.value = answer, I still need to do a manual keypress on the form to have it work, which isn't suited for my needs of automation.

What I have tried so far:
- Filling in the form.value and firing a keypress/keydown/keyup afterwards.
- Filling in the form.value minus one letter and firing a keypress afterwards, corresponding to the letter that was missed out.

For some strange reason afterwards, as well, the enter key doesn't work to submit until I do the manual keypress.

Can anyone help me out? Thanks!

• javascript
• reactjs
• google-chrome
• google-chrome-devtools

• document.execCommand with insertText parameter usually solves this. See examples and documentation. – woxxom Commented Apr 26, 2018 at 5:32

1 Answer 1

Better dirty way for filling form fields I use this when doing dirty browser testing of forms

Adapted from Here

Updated July 2023 to include select and checkboxes

const setFormFields = (formFields) => {
    const inputTypes = [
        window.HTMLInputElement,
        window.HTMLSelectElement, 
        window.HTMLTextAreaElement
    ];

const triggerInputChange = (selector, value) => {
    const node = document.querySelector(selector);
    // only process the change on elements we know have a value setter in their constructor
    if (inputTypes.indexOf(node.__proto__.constructor) > -1) {
        const setValue = Object.getOwnPropertyDescriptor(node.__proto__, 'value').set;
        let event = new Event('input', {
            bubbles: true
        });

        if(node.__proto__.constructor === window.HTMLSelectElement){
            event = new Event('change', {
                bubbles: true
            });
        } else if (node.type === 'checkbox') {
            node.checked = value;
            event = new Event('change', {
                bubbles: true
            });
        }
        setValue.call(node, value);
        node.dispatchEvent(event);
    }
    }

    Object.entries(formFields).forEach(([selector, value]) => triggerInputChange(selector, value));
}

// Usage:
setFormFields({
    '.substrate': '20',
    'name="first_name"': 'McFirsty',
    'name="last_name"': 'McLasty',
    'name="accept_terms"': true, // for checkboxes, use true for checked and false for unchecked
    'name="state"': 'VA' // for select boxes, use the value of the option you want to select
});

Addressing the specific question

document.querySelector('input').focus();
document.execCommand('insertText', false, 'Some Text For the Input');

Or if you want to replace the text every time

document.querySelector('input').select();
document.execCommand('insertText', false, 'Some Text For the Input');

I have a chrome script dev tools -> sources -> scripts that I use when doing dirty tests of forms

(()=>{
    const fillText = (selector, value) => {
        document.querySelector(selector).select();
        document.execCommand('insertText', false, value);
    }

    const formFields = [
        ['[data-ref-name="pany"]', 'My Company'],
        ['[data-ref-name="first_name"]', 'Styks']
    ]

    formFields.forEach(field => fillText(field[0], field[1]));
}
)()