Map loop javascript in function not returning desired value

Question

I have an array that contains objects that looks like this.

const arr = [
    {
        value: -1,
        label: "None"
    },
    {
        value: 24*60*60,
        label: "24 hours"
    },
    {
        value: 7*24*60*60,
        label: "7 days"
    },
    {
        value: 30*24*60*60,
        label: "1 month"
    },
    {
        value: 90*24*60*60,
        label: "3 months"
    }
];

I have the below function which 'kind of' works, but it is not returning the value. Can anyone spot what I am doing wrong?

The following is a react method

class Test extends Component { 

    ......

   getLabelFromValue(arr, value) {

      arr.forEach((item) => {

        if(item.value === value) {

            return item.label;

        }


    });

}

const value = getLabelFromValue(arr, 86400); //value is equal to undefined

getLabelFromValue(arr, value) { should be function getLabelFromValue(arr, value) { — Ionut Necula
– Ionut Necula, Commented Mar 10, 2017 at 9:05
You are using forEach and not map and not returning anything frm getLabelFromValue? — TryingToImprove
– TryingToImprove, Commented Mar 10, 2017 at 9:05

Community · Accepted Answer · 2017-05-23 10:30:05Z

2

Callum Linington has already given a short explanation and solution how to solve the problem with your .forEach() construct.

Based on the code, getLabelFromValue should return a single value only.
Hence I would use another method of Array -> Array.prototype.find

"The find() method returns the value of the first element in the array that satisfies the provided testing function. Otherwise undefined is returned."

getLabelFromValue(arr, value) {
    let item = arr.find(i => i.value === value);
    return item ? item.label : undefined /* or any other default value... */;
}

edited May 23, 2017 at 10:30

CommunityBot

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answered Mar 10, 2017 at 9:29

Andreas

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Comments

Callum Linington · Accepted Answer · 2017-03-10 09:26:09Z

2

You're returning from the forEach not the outer function:

getLabelFromValue(arr, value) {
    let label;
    let done = false;

    arr.forEach(item => {

        if(item.value === value && !done) {

            label = item.label;

            done = true;

        }


    });

    return label;
}

const value = getLabelFromValue(arr, 86400); //value is equal to undefined

I would personally just use filter.

arr.filter(item => item.value === value)[0]; // OR
arr.find(item => item.value === value);

edited Mar 10, 2017 at 9:26

answered Mar 10, 2017 at 9:04

Callum Linington

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