如何检查localStorage中值的重复

Question

我只想存储一次localStorage值。如果它存在localStorage，则应显示警告。

Answer 1

if(localStorage.getItem('item') != null){
   alert('in localStorage');
}
else{
   alert('not in localStorage');
}

Answer 2

这很简单。

只需检查密钥是否存在于localStorage中，如果不存在则添加密钥：

if(localStorage["keyName"]){
    alert("The key is stored");
}else{
    localStorage["keyName"] = "value";
}