从本地存储javascript中的对象数组中删除对象

Question

I have an array of objects in local storage like this:

ios = [{
    "id" : 1,
    "type" : "in",
    "cat" : "Diversi",
    "qty" : 50,
    "date" : "2016-11-02T09:51:48.872Z",
    "descr" : ""
  }, {
    "id" : 1,
    "type" : "in",
    "cat" : "Lavoro",
    "qty" : 50,
    "date" : "2016-11-02T10:08:11.362Z",
    "descr" : ""
  }];

I want to delete one of the objects with this function:

function remove(io) {
    var ios = localStorage.getItem('ios') ? JSON.parse(localStorage.getItem('ios')) : [];
    var index;
    for (var i = 0; i < ios.length; i++) {
        if (ios[i] === io) {
          index=i;
          break;
        }
    }
    ios.splice(index, 1);
    localStorage.setItem('ios', JSON.stringify(ios));
}

But when i call the function, and pass it the parameter to delete, it doesn't delete the one I want, but the first one in local storage instead. Can anyone help me please?

Answer 1

You can't test 2 objects being equal by using === . Try to use this function:

function isEquivalent(a, b) {
    var aProps = Object.getOwnPropertyNames(a);
    var bProps = Object.getOwnPropertyNames(b);

    if (aProps.length != bProps.length) {
        return false;
    }

    for (var i = 0; i < aProps.length; i++) {
        var propName = aProps[i];

        if (a[propName] !== b[propName]) {
            return false;
        }
    }

    return true;
}

And instead ios[i] === io , you call isEquivalent(ios[i],io) .

Answer 2

This is because your condition never get satisfied, so your index variable is always undefined ... So either pass some unique key value in the object like "id" and compare that key value pair like :-

function remove(id) {
    var ios = localStorage.getItem('ios') ? JSON.parse(localStorage.getItem('ios')) : [];
    var index;
    for (var i = 0; i < ios.length; i++) {
        if (ios[i].id === id) {
          index=i;
          break;
        }
    }
    if(index === undefined) return 
    ios.splice(index, 1);
    localStorage.setItem('ios', JSON.stringify(ios));
}

OR

use some third party like LODASH Doc as:-

function remove(io) {
        var ios = localStorage.getItem('ios') ? JSON.parse(localStorage.getItem('ios')) : [];
        var index;
        index = _.findIndex(ios , io);
        if(index === -1) return 
        ios.splice(index, 1);
        localStorage.setItem('ios', JSON.stringify(ios));
    }

Answer 3

You can use map function as,

function removeItem() {    
  var ios = JSON.parse(localStorage.getItem('ios'));
  var index = ios.map(function(element) {
    return element.cat;
  }).indexOf(io.cat);
  ios.splice(index, 1);
  localStorage.setItem('ios', JSON.stringify(ios));
}

to remove item based on passed object's cat in the array. Sample