Constant SELECT_ALL_JS 

pub const SELECT_ALL_JS: &str = r#"
(function(clear) {
    const el = this;
    const tag = (el.tagName || '').toLowerCase();
    if (tag === 'input' || tag === 'textarea') {
        if (clear) {
            el.value = '';
            el.dispatchEvent(new Event('input', { bubbles: true }));
            el.dispatchEvent(new Event('change', { bubbles: true }));
        } else {
            try { el.select(); } catch (e) {
                try { el.setSelectionRange(0, el.value.length); } catch (e2) {}
            }
        }
        return 'field';
    }
    if (el.isContentEditable) {
        if (clear) {
            el.textContent = '';
            el.dispatchEvent(new InputEvent('input', { bubbles: true }));
        } else {
            const sel = window.getSelection();
            sel.removeAllRanges();
            const range = document.createRange();
            range.selectNodeContents(el);
            sel.addRange(range);
        }
        return 'contenteditable';
    }
    return 'other';
})
"#;

Called via Runtime.callFunctionOn with this bound to the element about to receive typed text. Selects the element’s current content so the following Input.insertText replaces it (like Playwright fill). With clear=true the content is emptied outright and input/change are dispatched, for the “type an empty string” case.