Find JSON Object using multiple key/value pairs, then update that Object's other attribute

Question

Given

sessionStorage.cart = "[
  {"id":121,"name":"Pants","number":1,"specification":""},
  {"id":121,"name":"Pants","number":2,"specification":""},       
  {"id":121,"name":"Pants","number":3,"specification":""}
]"

I'd like to write a function that finds the object with id of 121, name of Pants, number of 2, so that I can update that object's specification. So I would pass the id, the name, the number, and the desired new specification value, and get an output of this:

sessionStorage.cart = "[
  {"id":121,"name":"Pants","number":1,"specification":""},
  {"id":121,"name":"Pants","number":2,"specification":"new value"},       
  {"id":121,"name":"Pants","number":3,"specification":""}
]"

Am really struggling on thinking this one through... guidance welcome!

The question is using an array in the example, not JSON which is making the answers below incorrect. — obreezy
– obreezy, Commented Oct 27, 2018 at 14:49

iplus26 · Accepted Answer · 2015-08-07 02:52:08Z

5

Use this:

var cart = [
    {
        "id": 121,
        "name": "Pants",
        "number": 1,
        "specification": ""
    },
    {
        "id": 121,
        "name": "Pants",
        "number": 2,
        "specification": ""
    },
    {
        "id": 121,
        "name": "Pants",
        "number": 3,
        "specification": ""
    }
];

cart.forEach(function(entry) {
    if (entry.id == 121 && entry.name == 'Pants' && entry.number == 2) {
        entry.specification = 'new value';
    }
});

console.log(cart);

answered Aug 7, 2015 at 2:52

iplus26

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Comments

Mulan · Accepted Answer · 2015-08-07 03:38:56Z

1

A simple solution using Array.prototype.find

sessionStorage.cart.find(e => 
  e.id     === 121     &&
  e.name   === 'Pants' &&
  e.number === 2
).specification = 'new value';

console.log(JSON.stringify(sessionStorage.cart, null, '  '));

Output

[
  {
    "id": 121,
    "name": "Pants",
    "number": 1,
    "specification": ""
  },
  {
    "id": 121,
    "name": "Pants",
    "number": 2,
    "specification": "new value"
  },
  {
    "id": 121,
    "name": "Pants",
    "number": 3,
    "specification": ""
  }
]

Note: This requires ES6.

answered Aug 7, 2015 at 3:38

Mulan

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Comments

Neil Villareal · Accepted Answer · 2015-08-07 03:31:24Z

0

You might want to try this code:

function update(oldValues, newValues, keyToCompare) {
    var keyToCompareLen = keyToCompare.length;
    var result = [];
    oldValues.forEach(function(oldValue){

        newValues.forEach(function(newValue){
            var cnt = 0;
            keyToCompare.forEach(function(key){
                if(newValue[key] == oldValue[key]) {
                    ++cnt;
                }
            });

            if(cnt == keyToCompareLen) {
                oldValue = $.extend(true, {}, oldValue, newValue);
            }
        });

        result.push(oldValue);
    });

    return result;
}

var result = update([
  {"id":121,"name":"Pants","number":1,"specification":""},
  {"id":121,"name":"Pants","number":2,"specification":""},       
  {"id":121,"name":"Pants","number":3,"specification":""}
], [
  {"id":121,"name":"Pants","number":2,"specification":"test"}
], [
  "id",
  "name",
  "number"
]);

console.log(result);

Note: You need to include the jquery library. You can also run the code here https://fiddle.jshell.net/b17fx6qk/1/

edited Aug 7, 2015 at 3:31

answered Aug 7, 2015 at 2:59

Neil Villareal

6379 silver badges14 bronze badges

3 Comments

iplus26 Over a year ago

I think it's a little over to use jQuery for only jQuery.extend() method while you don't use it in other places.

Neil Villareal Over a year ago

@iplus26, No problem to that because he/she is already using a jquery library.

iplus26 Over a year ago

No, no, no. Don't get me wrong. I just want to discuss when to use jQuery... It's nothing personal, sorry...

rrowland · Accepted Answer · 2015-08-07 03:42:32Z

0

Iterating through an array can be inefficient. For performance, you could stringify all of your index values and use them to store your objects in a hashmap for a quick lookup. Something like:

function cartItem() {
  this.id;
  this.name;
  this.number;
  this.specification;
}

CartItem.hash = function(id, name, number) {
  return [id, name, number].join('|');
};

cartItem.prototype.toHash = function() {
  return CartItem.hash(this.id, this.name, this.number);
};

var cartMap = cart.reduce(function(map, item) {
  var key = item.toHash();
  map[key] = item;
}, { });

Then you can (very quickly) look the item up by its hash:

cartMap[CartItem.hash(id, name, number)];

answered Aug 7, 2015 at 3:42

rrowland

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Comments

user786 · Accepted Answer · 2015-08-07 03:51:20Z

Try doing this. Simply match and update

$(document).ready(function() {

  var o = [];
  o.id = 121;
  o.name = "Pants";
  o.number = 2;

  updateVal(o);

});


function updateVal(o) {

  var cart = [{
    "id": 121,
    "name": "Pants",
    "number": 1,
    "specification": ""
  }, {
    "id": 121,
    "name": "Pants",
    "number": 2,
    "specification": ""
  }, {
    "id": 121,
    "name": "Pants",
    "number": 3,
    "specification": ""
  }];

  $.each(cart, function(a, b) {

    if (b.id == o.id && b.name == o.name && b.number == o.number) {
      b.specification = "new value";
    }


  });

  alert("value updated. specification:" + cart[1].specification);

}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

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