你可以使用hasOwnProperty方法来检查

> localStorage.setItem('foo', 123)
undefined
> localStorage.hasOwnProperty('foo')
true
> localStorage.hasOwnProperty('bar')
false

适用于当前版本的Chrome(Mac)， Firefox(Mac)和Safari。

为真正的

localStorage.infiniteScrollEnabled = 1;

因为假

localStorage.removeItem("infiniteScrollEnabled")

检查存在

if (localStorage[""infiniteScrollEnabled""]) {
  //CODE IF ENABLED
}

最短的方法是使用默认值，如果key不在存储中:

var sValue = localStorage['my.token'] || ''; /* for strings */
var iValue = localStorage['my.token'] || 0; /* for integers */

我能建议的最好最安全的方法就是，

if(Object.prototype.hasOwnProperty.call(localStorage, 'infiniteScrollEnabled')){
    // init variable/set default variable for item
    localStorage.setItem("infiniteScrollEnabled", true);
}

这将通过ESLint的no-prototype-builtins规则。

我在这里添加了一些方法来检查

方法1

if("infiniteScrollEnabled" in localStorage){
     console.log("Item exists in localstorage");
}else{
    console.log("Item does not exist in localstoarge";
}

方法2

if(localStorage.getItem("infiniteScrollEnabled") === null){
    console.log("Item does not exist in localstoarge";
}else{
   console.log("Item exists in localstorage");
}

方法3

if(typeof localStorage["cart"] === "undefined"){
    console.log("Item does not exist in localstoarge";
}else{
   console.log("Item exists in localstorage");
}

方法4

if(localStorage.hasOwnProperty("infiniteScrollEnabled")){
     console.log("Item exists in localstorage");
 }else{
    console.log("Item does not exist in localstoarge";
 }

如果你想检查undefined，你也可以试试这个:

if (localStorage.user === undefined) {
    localStorage.user = "username";
}

getItem是一个方法，如果没有找到value则返回null。