Custom button block doesn't work

I am a beginner in creating Gutenberg blocks. I want to create a custom block for a button. It should have an input field inside for the button text and the user should be able to choose between two button styles and the target URL in the InspectorControls area. But somehow my code doesn't work. The editor refreshes when I am inside of the input field and I am not able to access InspectorControls. Here is my code:

const InspectorControls = wp.editor.InspectorControls;
const PanelBody = wp.components.PanelBody;
const PanelRow = wp.components.PanelRow;
const RadioControl = wp.components.RadioControl;
const TextControl = wp.components.TextControl;


wp.blocks.registerBlockType('test-blocks/primary-button', {
    title: 'Primary Button',
    icon: 'button',
    category: 'test',
    attributes: {
        buttonText: {
            type: 'string'
        },
        buttonLink: {
            type: 'string'
        },
        buttonStyle: {
            type: 'string',
            default: btn btn-primary
        }
    },
    edit: function (props) {
        use strict;

        function updateText(event) {
            props.setAttributes({
                buttonText: event.target.value
            });
        }

        function updateLink(event) {
            props.setAttributes({
                buttonLink: event.target.value
            });
        }

        function updateStyle(event) {
            props.setAttributes({
                buttonStyle: event.target.value
            });
        }
        return wp.element.createElement(
            div,
            null,
            wp.element.createElement(
                a, {
                    type: button,
                    href: ,
                    class: props.attributes.buttonStyle
                },
                wp.element.createElement(input, {
                    type: text,
                    value: props.attributes.buttonText,
                    onChange: updateText
                })
            ),
            wp.element.createElement(
                InspectorControls,
                null,
                wp.element.createElement(
                    PanelBody, {
                        title: Button Settings,
                        initialOpen: true
                    },
                    wp.element.createElement(
                        PanelRow,
                        null,
                        wp.element.createElement(RadioControl, {
                            label: Button Style,
                            value: props.attributes.buttonStyle,
                            options: [{
                                    label: Primary,
                                    value: btn btn-primary
                                },
                                {
                                    label: Secondary,
                                    value: btn btn-secondary
                                }
                            ],
                            onChange: updateStyle
                        })
                    ),
                    wp.element.createElement(
                        PanelRow,
                        null,
                        wp.element.createElement(TextControl, {
                            label: Target URL,
                            value: props.attributes.buttonLink,
                            onChange: updateLink
                        })
                    )
                )
            )
        );


    },
    save: function (props) {
        use strict;
        return wp.element.createElement(a, {
            type: button,
            href: props.attributes.buttonLink,
            class: props.attributes.buttonStyle
        }, props.attributes.buttonText);
    }
});