如何测试本地存储阵列中是否已经存储了特定的对象属性值

Question

I have two input values in my HTML, siteName and siteUrl and I am asigning them to two objects property (name:siteName, url:siteUrl). Then after object was created I am pushing it to an array and storing into browsers local storage, but before it goes to local storage I want to test object property name value and if it is already there to alert me

This is my code for now...

//get site name and site url
var siteName = document.getElementById('siteName').value; 
var siteUrl = document.getElementById('siteUrl').value;

var bookmark = {

  name:siteName,
  url:siteUrl
}

/test if item bookmarks is null
if(localStorage.getItem('bookmarks') === null){

//Initiate Array
var bookmarks = [];

//add to array
bookmarks.push(bookmark);

//set to local storage
localStorage.setItem('bookmarks', JSON.stringify(bookmarks));


//get bookmarks from local storage
}else{
var bookmarks = JSON.parse(localStorage.getItem('bookmarks'));

//add bookmark in array
bookmarks.push(bookmark);


//re-set back to local storage
localStorage.setItem('bookmarks', JSON.stringify(bookmarks));

}

Answer 1

you can it by using .length The length property returns the number of elements in an array. And .valueOf() method return value of string object but .valueOf() you can't use explicitly in your code.

Answer 2

There are two ways to do this.

1st method-

//get localstorage value
var bookmarks = JSON.parse(localStorage.getItem('bookmarks'));
var flagExists = false;

if(bookmarks != null && bookmarks.length > 0){
    for(var i=0; i<bookmarks.length; i++){
        var existingBookmark = bookmarks[i];
        //check if your current value against key name is already present in any existing bookmar 
        if(bookmark.name === existingBookmark.name){
            //do anything that you want here
            flagExists = true;
            break;
        }
    }
}

2nd Method is to use Lodash Library. With lodash you can do this in one line.

//get localstorage value
var bookmarks = JSON.parse(localStorage.getItem('bookmarks'));
var flagExists = false;
var _ = require("lodash");

if(bookmarks != null && bookmarks.length > 0){
    var flagExists = _.find(bookmarks, {'name': bookmark.name}) != null;
    //do whatever you want
}