JSFiddle - React, Tailwind, and code Playground

HTML

<div class="showbutton02">
            <form action="/take-away/?add-to-cart=79" class="cart myform" method="post" enctype="multipart/form-data">
                <div class="quantity buttons_added"><input type="button" value="-" class="minus"><input type="number" step="1" name="quantity" value="1" title="Qty" class="input-text qty text"><input type="button" value="+" class="plus"></div>
<div class="linkbtn02"><button type="submit" data-product_id="79" data-product_sku="" data-quantity="1" class="add_to_cart_button button product_type_simple">Add to cart</button></div>            </form>
            </div>

CSS

.minus, .qtyminus {
width: 25px;
height: 25px;
float: left;
background: #e8e8e8;
border: none;
font-size: 14px;
color: #000;
}
.plus, .qtyplus {
width: 25px;
height: 25px;
float: left;
background: #e8e8e8;
border: none;
font-size: 14px;
color: #000;
}
.linkbtn02 button {
background: none repeat scroll 0 0 #000000;
border: medium none;
color: #FFFFFF;
display: inline-block;
font-family: 'RalewaySemiBold';
font-size: 14px;
letter-spacing: 2px;
margin: 0;
outline: medium none;
padding: 4px 10px 3px;
text-transform: uppercase;
}

JavaScript

jQuery(document).ready(function($) {


	$(document).on( 'click', '.plus, .minus', function() {

		// Get values
		var $qty 		= $(this).closest('.quantity').find(".qty");
	    var currentVal 	= parseFloat( $qty.val() );
	    var max 		= parseFloat( $qty.attr('max') );
	    var min 		= parseFloat( $qty.attr('min') );
	    var step 		= $qty.attr('step');

	    // Format values
	    if ( ! currentVal || currentVal == "" || currentVal == "NaN" ) currentVal = 0;
	    if ( max == "" || max == "NaN" ) max = '';
	    if ( min == "" || min == "NaN" ) min = 0;
	    if ( step == 'any' || step == "" || step == undefined || parseFloat( step ) == "NaN" ) step = 1;

	    // Change the value
	    if ( $(this).is('.plus') ) {

		    if ( max && ( max == currentVal || currentVal > max ) ) {
		    	$qty.val( max );
		    } else {
		    	$qty.val( currentVal + parseFloat( step ) );
		    }

	    } else {

		    if ( min && ( min==currentVal || currentVal < min ) ) {
		    	$qty.val( min );
		    } else if ( currentVal > 0 ) {
		    	$qty.val( currentVal - parseFloat( step ) );
		    }

	    }

	    // Trigger change event
	    $qty.trigger('change');
	});


});