CODEWITHSUNDEEP
javascriptlodash
realtebo
realtebo

Reputation: 25645

Lodash map with function: how to pass to function another parameter?

I'm using lodash map in this way 

const newCollection = _.map(
    responseJson.OldCollection, 
    AddDetailsToSingleItems
);

having

function AddDetailsToSingleItems (item ) {
 ... 
}

I ask you, please, what's the right syntax to pass a parameter to this function.

I'd like to have

function AddDetailsToSingleItems (item, myNewParam ) {
 ... 
}

(note the myNewParam).

I don't kow how to tell to loadsh map to pass every single item to my function and to pass one more param when calling AddDetailsToSingleItems

Upvotes: 4

Views: 3637

Answers (2)

Mike K
Mike K

Reputation: 629

You can create a function that knows the value of myNewParam, but only accepts the item parameter like this:

var myNewParam = 'param_value';

var AddDetailsFn = function(m) {
  return function(item) {
    return AddDetailsToSingleItems(item, m);
  };
};

const newCollection = _.map(
    responseJson.OldCollection, 
    AddDetailsFn(myNewParam)
);

This way, _.map only sees a function that takes a single parameter. The AddDetailsFn returns a function that takes a single parameter, but already has the value of myNewParam captured. You can also be more succinct with:

const newCollection = _.map(
    responseJson.OldCollection,
    function(item) { return AddDetailsToSingleItems(item, myNewParam); }
);

Upvotes: 2

Hunter McMillen
Hunter McMillen

Reputation: 61512

You haven't explained where myNewParam is coming from, but I assume you have that data somewhere.

Lodash map (just like normal JavaScript map) accepts a function as its second argument to be run on all elements of the supplied list. You can just pass an anonymous function: 

_.map(
  responseJson.OldCollection, 
  item => AddDetailsToSingleItems(item, myNewParam)
);

Upvotes: 5

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