JS: Array defined or undefined

Question

I have data like,

data = [cluster1:skill1, cluster1:skill2, cluster1:skill3, cluster2, cluster3:skill4, cluster4:skill5];

From the above lookup I am modeling data like below structure using the code I tried,

modelData 
    [0]: 
        Main: cluster1
        Sub: skill1,skill2,skill3

    [1]:
        Main: cluster2
        Sub: //want this to be empty but now it is undefined
    [2]:
        Main: cluster3
        sub: skill4,skill5
// code JS
    dataMap = data().reduce(function (map, item) {
        var key = item.split(':')[0];
        map[key] = map[key] || [];
        map[key].push(item.split(':')[1]);
        return map;
    }, {});

    modelData(Object.keys(dataMap).map(function(key) {
            return {
                Main: ko.observable(key),
                Sub: ko.observableArray(dataMap[key])
        };
    }));

All I want is if an lookup entry doesnot contains : (colon), then that entry should be considered as Main value and sub array should be empty rather than undefined. I am confused that how can I check that sub array is undefined or defined.

Any suggestion would be helpful

please add some real data. please have a look here: minimal reproducible example — Nina Scholz
– Nina Scholz, Commented Dec 22, 2016 at 9:04
Can you format you data to reflect actual content in it.. at the moment its not even valid data.. — Rajshekar Reddy
– Rajshekar Reddy, Commented Dec 22, 2016 at 9:04

Rajshekar Reddy · Accepted Answer · 2016-12-22 09:14:01Z

1

I am confused that how can I check that sub array is undefined or defined.

Looking at your code All you need is to replace this line

 map[key].push(item.split(':')[1]); // your element at [1] might be undefined

With

 map[key].push(item.split(':')[1] || []); // if [1] is undefined push [] empty array

You need to check if the data you are trying to push is undefined or not. You can do that by using || operator.

edited Dec 22, 2016 at 9:14

answered Dec 22, 2016 at 9:06

Rajshekar Reddy

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4 Comments

Jeya Suriya Muthumari Over a year ago

This is really awesome! I tried, It is adding empty value with array length 1. I dont even want this empty value pushed array. I just want this array to be empty with length 0. Is there any way to do this.

Rajshekar Reddy Over a year ago

@MJSuriya replace "" with [] .. Let me know if that is what you are looking for

Jeya Suriya Muthumari Over a year ago

That's amazing ! Thanks a lot

Rajshekar Reddy Over a year ago

@MJSuriya glad to help!!

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