1

I have this javascript object:

{"Vanilla": 36, "Chocolate": 50, "Stracciatella": 24, "Coffee": 18}

to which I would like to "add" this array:

["Vanilla", "Amarena", "Chocolate", "Pistachio"]

The result I want is this:

{
    "Vanilla": 37,
    "Chocolate": 51,
    "Stracciatella": 24,
    "Coffee": 18,
    "Amarena": 1,
    "Pistachio": 1
}

This is what I have tried:

var me = ["Vanilla", "Amarena", "Chocolate", "Pistachio"]
var all = {
    "Vanilla": 36,
    "Chocolate": 50,
    "Stracciatella": 24,
    "Coffee": 18
}
var keys = Object.keys(all);
for (var i = 0; i < me.length; i++) {
    if (me[i] in keys) {
        console.log("keys:" + keys + " - " + me[i] + " in keys");
    } else {
        console.log("keys:" + keys + " - " + me[i] + " not in keys");

    };
}

console.log(keys);
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1
  • 1
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4 Answers 4

Reset to default
4

This works

the first part of the code in your fiddle

var me = ["Vanilla", "Amarena", "Chocolate", "Pistachio"]
var all = {
    "Vanilla": 36,
    "Chocolate": 50,
    "Stracciatella": 24,
    "Coffee": 18
}

Now the answer:

me.forEach(function(key) { // forEach iterates through an array 
    all[key] = (all[key] || 0) + 1; // create new item if it doesn't exist
});

The forEach() method executes a provided function once per array element.

For a more detailed description of .forEach see MDN documentation where the above description came from

as this question was tagged jQuery, lets add some jQuery code, just for laughs

$.each(me, function(unusedIndex, key) {
    all[key] = (all[key] || 0) + 1;exist
});

jQuery.each() A generic iterator function, which can be used to seamlessly iterate over both objects and arrays. Arrays and array-like objects with a length property (such as a function's arguments object) are iterated by numeric index, from 0 to length-1. Other objects are iterated via their named properties. - source http://api.jquery.com/jquery.each/

Here's me playing with myself - http://jsfiddle.net/7ephp3f4/1/

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6 Comments

although this answer is more elegant it does not take into account the coding level the OP obviously has. therefore the answer from @anthony-blackshaw is better suited as answer for this specific post.
@hurrtz So make this level higher. Array methods are as primitive knowledge as simple loops. Both are not quantum mechanics. So this answer makes as much sense as the the with for-loop.
@JaromandaX Care you elaborate what .forEach is and how it works?
Fine answer anyway, omitting comments. Use all[key]++ to kill one byte more.
I agree. Apart from the commenting this is a very nice approach. Thanks for going into detail about the mechanics. +1
|
3

The following code allows you to increment the values within your object stock based on the keys in your array stockUpdate:

var stockUpdate = ["Vanilla", "Amarena", "Chocolate", "Pistachio"];
var stock = {
    "Vanilla": 36,
    "Chocolate": 50,
    "Stracciatella": 24,
    "Coffee": 18
};

for (var i=0; i < stockUpdate.length; i++) {
    var stockType = stockUpdate[i];
    if (stock[stockType] === undefined) {
        stock[stockType] = 0;
    }
    stock[stockType]++;
}
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Comments

1

you are almost there, 

var me = ["Vanilla", "Amarena", "Chocolate", "Pistachio"]
var all = {
    "Vanilla": 36,
    "Chocolate": 50,
    "Stracciatella": 24,
    "Coffee": 18
}
var keys = Object.keys(all);
for (var i = 0; i < me.length; i++) {
    if (keys.indexOf(me[i]) >= 0) {
        console.log("keys:" + keys + " - " + me[i] + " in keys \n");
        all[me[i]]++;
    } else {
        console.log("keys:" + keys + " - " + me[i] + " not in keys \n");
        all[me[i]] = 1;
    };
}

console.log(all);

you can also use reduce to "merge" the newItems into items

var items = {"Vanilla": 36, "Chocolate": 50, "Stracciatella": 24, "Coffee": 18}
var newItems = ["Vanilla", "Amarena", "Chocolate", "Pistachio"];

var result = newItems.reduce(function(pre, curr) {
        // use double == to check when the item is either undefined or null
        pre[curr] = (pre[curr] == null? 0 : pre[curr]) + 1;
        return pre;
// pass items as the initial data to reduce
}, items);

console.log(result);

The reduce() method applies a function against an accumulator and each value of the array (from left-to-right) to reduce it to a single value.

in this case, I reduce the newItems list, from left to right, calcuate the count in the items object, and return the calculated items.

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1 Comment

In the end, I kept experimenting and used reduce. +1 for the encouragement!
0

It is a good moment to use http://underscorejs.org:

var me = ["Vanilla", "Amarena", "Chocolate", "Pistachio"];

var all = {
  "Vanilla": 36,
  "Chocolate": 50,
  "Stracciatella": 24,
  "Coffee": 18
};

_.each(me, function(name) {
  if (_.has(all, name)) {
    all[name]++;
  } else {
    all[name] = 1;
  }
});
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1 Comment

Still counting bytes? Underscore is powerful common inventory to manipulate arrays and objects, it may be useful in other cases of the project.

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