window.onload = function(){
var price = document.getElementById('price');
price.disabled = true;
price.style.padding = '2px 3px';
price.style.background = '#eee';
price.style.border = '1px solid #ccc';
var tj = document.getElementById('tj');
tj.onclick = function(){
if(tj.checked == true){ //可编辑
price.disabled = false;
price.style.background = '#fff';
price.style.border = '2px solid #ff7d00';
price.style.padding = '2px 3px';
price.focus();
} else {
price.disabled = true;
price.style.background = '#eee';
price.style.border = '1px solid #ccc';
price.style.padding = '2px 3px';
}
}
}
<form action="#">
价格：<input id="price" type="text"> <input id="tj" hidefocus=true type="checkbox">特价
</form>
唯一的可去之外是加了一点美化，使用户体验更加一层楼，其中包括边框的加粗，焦点的获取，checkbox边框线的隐藏等等。
测试代码