通过“添加”数组来增加Javascript对象的值

Question

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);

Answer 1

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]++;
}

Answer 2

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/

Answer 3

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.

Answer 4

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;
  }
});