JavaScript compare two arrays(key/value pairs) and copy value from one to the other if key matches

Question

I have two arrays containing key/value pairs.

{
    "containerOne": [{
        "Id": 1,
            "Title": "TitleOne",
            "Responsibility": "ValueOne"
    }, {
        "Id": 2,
            "Title": "TitleTwo",
            "Responsibility": "ValueTwo"
    }]
}

{
    "containerTwo": [{
        "Id": 1,
            "Title": "TitleOne",
            "Responsibility": null
    }, {
        "Id": 2,
            "Title": "TitleTwo",
            "Responsibility": "null         
                               }
            ]
    }

I'd like to compare both arrays and compare the title of each container. If the titles match, then I'd like to copy the Responsibility value from containerOne to containerTwo. The ID's will not match, so that can be ruled out. Only the titles will be consistent.

What is the most efficient way to do this please?]

Thanks

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EDIT

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Looking at the arrays a little closer, there is a subtle difference in the data being returned:

{
"AMLookupTasksList":
    [
        {
            "Id":1,
            "Title":"Create and Maintain an Onboarding Document",
            "Responsibility":"1. Onboarding|f101ccf1-c7d5-42e7-ba8f-48e88ac90a3d"
        },
        {
            "Id":2,
            "Title":"Execute Onboarding for New Consultants",
            "Responsibility":"1. Onboarding|f101ccf1-c7d5-42e7-ba8f-48e88ac90a3d"
        }
    ]

}

{
"AMTasksList":
    [
        {
            "Id":4,
            "Title":
                {
                    "$M_1":13,"$c_1":"Create and Maintain an Onboarding Document"
                },
            "Responsibility":null
        },
        {
            "Id":17,
            "Title":
                {
                    "$M_1":12,"$c_1":"Execute Onboarding for New Consultants"
                },
            "Responsibility":null
        }
    ]

}

Do I have additional looping to get to the Title value in the second array?

Answer 1

This might be a bit of overkill but it ignores the sequence and does a look up in each object. I had to fix some syntax in your objects but I include that: named the objects and took a quote off one of the null values.

var obj1 = {
    "containerOne": [{
        "Id": 1,
            "Title": "TitleOne",
            "Responsibility": "ValueOne"
    }, {
        "Id": 2,
            "Title": "TitleTwo",
            "Responsibility": "ValueTwo"
    }]
};
var obj2 = {
    "containerTwo": [{
        "Id": 1,
            "Title": "TitleOne",
            "Responsibility": null
    }, {
        "Id": 2,
            "Title": "TitleTwo",
            "Responsibility": null
    }]
};

Now the code:

// lookup for first object:
var lookup = {};
// create referece to list above and use it everywhere
lookup.list = obj1;
for (var i = 0, len = lookup.list.containerOne.length; i < len; i++) {
    lookup[lookup.list.containerOne[i].Title] = lookup.list.containerOne[i];
}
// lookup for second object
var otherLookup = {};
otherLookup.list = obj2;
for (var i = 0, len = otherLookup.list.containerTwo.length; i < len; i++) {
    otherLookup[otherLookup.list.containerTwo[i].Title] = otherLookup.list.containerTwo[i];
}

// copy value for Responsibility from first to second on each matched in second.
var i = 0;
var len = lookup.list.containerOne.length;
for (i; i < len; i++) {
    // looks up value from second list in the first one and if found, copies 
    if (lookup[otherLookup.list.containerTwo[i].Title]) {
        otherLookup.list.containerTwo[i].Responsibility = lookup[otherLookup.list.containerTwo[i].Title].Responsibility;
    }
}

// alerts new value using lookup
alert(otherLookup["TitleOne"].Responsibility);

EDIT for new structure, but same answer really:

var obj1 = {
    "AMLookupTasksList": [{
        "Id": 1,
            "Title": "Create and Maintain an Onboarding Document",
            "Responsibility": "1. Onboarding|f101ccf1-c7d5-42e7-ba8f-48e88ac90a3d"
    }, {
        "Id": 2,
            "Title": "Execute Onboarding for New Consultants",
            "Responsibility": "1. Onboarding|f101ccf1-c7d5-42e7-ba8f-48e88ac90a3d"
    }]
};
var obj2 = {
    "AMTasksList": [{
        "Id": 4,
            "Title": {
            "$M_1": 13,
                "$c_1": "Create and Maintain an Onboarding Document"
        },
            "Responsibility": null
    }, {
        "Id": 17,
            "Title": {
            "$M_1": 12,
                "$c_1": "Execute Onboarding for New Consultants"
        },
            "Responsibility": null
    }]
};

var lookup = {};
// create refernece to list above and use it everywhere
lookup.list = obj1;
for (var i = 0, len = lookup.list.AMLookupTasksList.length; i < len; i++) {
    lookup[lookup.list.AMLookupTasksList[i].Title] = lookup.list.AMLookupTasksList[i];
}
var otherLookup = {};
otherLookup.list = obj2;
for (var i = 0, len = otherLookup.list.AMTasksList.length; i < len; i++) {
    otherLookup[otherLookup.list.AMTasksList[i].Title.$c_1] = otherLookup.list.AMTasksList[i];
}

// copy value for Responsibility from first to second
var i = 0;
var len = otherLookup.list.AMTasksList.length;
for (i; i < len; i++) {
    if (lookup[otherLookup.list.AMTasksList[i].Title.$c_1]) {

        otherLookup.list.AMTasksList[i].Responsibility = lookup[otherLookup.list.AMTasksList[i].Title.$c_1].Responsibility;
    }
}

alert(otherLookup["Create and Maintain an Onboarding Document"].Responsibility);

Fiddle for second answer: http://jsfiddle.net/n22V8/

Answer 2

You should compare properties and set them as the following:

containerOne.innerContainer.forEach(function (element,index) {
    containerTwo.innerContainer.forEach(function (element2,index2) {
       if (element.Title === element2.Title && element.Property != element2.Property) {
           element2.Property = element.Property;
       }
    });
});

Answer 3

First, create a dictionary from containerTwo:

var c2dict = {};
var c2i = containerTwo.innerContainer;
for (var i = 0; i < c2i.length; i++) {
    c2dict[c2i[i].Title] = c2i[i];
}

Now use this to do the copying of propertyies when titles match:

var c1i = containerOne.innerContainer;
for (var i = 0; i < c1i.length; i++) {
    if (c2dict[c1i[i].Title]) {
        c2dict[c1i[i].Title].Property = c1i[i].Property;
    }
}