Guide on utilizing a variable as a property in the `indexOf` function within a `map` function

Question

Guide on utilizing a variable as a property in the `indexOf` function within a `map` function

I have a method that looks like this:

retrieveUniqueValues(param) {
    var uniqueValues = [];
    uniqueValues = this.state.DataObjects.map(item => {
        if (uniqueValues.indexOf(item[param]) === -1) {
            uniqueValues.push(item[param])
        }
    });
}

//DataObjects is an array of objects

DataObjects = [
    {tag: 23, name: vicky, gender: m},
    {tag: 13, name: sam, gender: m},
    {tag: 23, name: raj, gender: m}
]

//item can be any object as shown above
item = {tag: 23, name: vicky, gender: m}

The param here represents the property name such as tag.

Even though the param has a value before and after the map function, I am encountering it as undefined in the following line:

if (uniqueValues.indexOf(item[param]) === -1) { }

My goal is to retrieve unique values for any specific property, for example, for the tag: 23, 13. While using x.tag or x.name or x.gender works fine, I intend to make the property name dynamic.

javascript

Answer 1

Answer №1

In order to dynamically search for the key that matches the value stored in param, you can make the following adjustment:

if (list.indexOf(obj.param) === -1) {
    list.push(obj.param)
}

Rather than searching for a key named param, you should update it to:

if (list.indexOf(obj[param]) === -1) {
    list.push(obj[param])
}

This change allows you to check for keys with names matching the value of param.

Answer 2

In order to dynamically search for the key that matches the value stored in param, you can make the following adjustment:

if (list.indexOf(obj.param) === -1) {
    list.push(obj.param)
}

Rather than searching for a key named param, you should update it to:

if (list.indexOf(obj[param]) === -1) {
    list.push(obj[param])
}

This change allows you to check for keys with names matching the value of param.

Answer 3

Answer №2

CollectionData = [
    {id: 23, title: 'apple', category: 'fruit'},
    {id: 13, title: 'banana', category: 'fruit'},
    {id: 30, title: 'orange', category: 'fruit'}
]
output = _.map(CollectionData,'id'); //[23, 13, 30], check if ID exists in the array!
if(output.indexOf(23)===-1)
    outcome = 'missing';
else 
    outcome = 'present';

Answer 4

CollectionData = [
    {id: 23, title: 'apple', category: 'fruit'},
    {id: 13, title: 'banana', category: 'fruit'},
    {id: 30, title: 'orange', category: 'fruit'}
]
output = _.map(CollectionData,'id'); //[23, 13, 30], check if ID exists in the array!
if(output.indexOf(23)===-1)
    outcome = 'missing';
else 
    outcome = 'present';

Guide on utilizing a variable as a property in the `indexOf` function within a `map` function

Answer №1

Answer №2

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