CODEWITHSUNDEEP
javascriptfunctiondictionaryreduce
Vidhan Bagdai
Vidhan Bagdai

Reputation: 29

Javascript using a function Number() inside map() function to convert string to a number

I want to convert the imdb ratings given inside the array of objects watchList. I am trying it using map function but it is not happening. The newList is giving just the old list with no changes whatever. What am I doing wrong?

var watchList = [
                {  

                   "Metascore": "74",
                   "imdbRating": "8.8",
                   "imdbVotes": "1,446,708",
                   "imdbID": "tt1375666",
                   "Type": "movie",
                   "Response": "True"
                },
                {  
                   "Metascore": "74",
                   "imdbRating": "8.6",
                   "imdbVotes": "910,366",
                   "imdbID": "tt0816692",
                   "Type": "movie",
                   "Response": "True"
                },
                {
                   "Metascore": "82",
                   "imdbRating": "9.0",
                   "imdbVotes": "1,652,832",
                   "imdbID": "tt0468569",
                   "Type": "movie",
                   "Response": "True"
                }
];



let newList=[];
newList=watchList.map(function(list){
  Number(list.imdbRating);
  return list;
});
console.log(newList);

Upvotes: 2

Views: 1692

Answers (2)

CertainPerformance
CertainPerformance

Reputation: 371019

Just declaring Number does not mutate the original value. If you want the object's property to have its imdbRating be a Number, you have to assign it.

var watchList=[{"Metascore":"74","imdbRating":"8.8","imdbVotes":"1,446,708","imdbID":"tt1375666","Type":"movie","Response":"True"},{"Metascore":"74","imdbRating":"8.6","imdbVotes":"910,366","imdbID":"tt0816692","Type":"movie","Response":"True"},{"Metascore":"82","imdbRating":"9.0","imdbVotes":"1,652,832","imdbID":"tt0468569","Type":"movie","Response":"True"}];

watchList.forEach(function(list){
  list.imdbRating = Number(list.imdbRating);
});
console.log(watchList);

Note that objects are passed by reference in Javascript - changing something in a reference to an object will change the original object, which is why I used forEach instead of .map. If you want to create entirely new objects (and not mutate the original ones), use object spread as well as map:

var watchList=[{"Metascore":"74","imdbRating":"8.8","imdbVotes":"1,446,708","imdbID":"tt1375666","Type":"movie","Response":"True"},{"Metascore":"74","imdbRating":"8.6","imdbVotes":"910,366","imdbID":"tt0816692","Type":"movie","Response":"True"},{"Metascore":"82","imdbRating":"9.0","imdbVotes":"1,652,832","imdbID":"tt0468569","Type":"movie","Response":"True"}];

const newList = watchList.map(({ imdbRating, ...rest }) => ({
  imdbRating: Number(imdbRating),
  ...rest,
}));
console.log(newList);

Upvotes: 1

sefa
sefa

Reputation: 504

If you want a quick conversion from string to integer you can use + operator.

Example :

var newList=[];
newList=watchList.map(function(list){
    list.imdbRating = +list.imdbRating;  
    return list;
});

Upvotes: 0

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