CODEWITHSUNDEEP
javascriptjquerydictionary
mithril333221
mithril333221

Reputation: 819

understanding jQuery map

I found this example that says:

var arr=$.map([0,1,2],function(n){
    return [n,n+1];
});

Will make arr a 6 item array. However, I don't understand why it isn't [[x,y],[x,y],[x,y]]

I need to know step by step what just happened. This map functions seems very useful, I would hate to don't use it simply because I don't understand its behavior.

Upvotes: 2

Views: 247

Answers (3)

user1106925
user1106925

Reputation:

You can double wrap the returned Array to avoid the flattened output.

var arr=$.map([0,1,2],function(n){
     //    v--------------v----- flattened
    return [ [ n, n + 1 ] ];
     //      ^----------^------- inserted
});

arr;  // [[0,1],[1,2],[2,3]]

IMO, you'll be better off using a standard .map() function instead of jQuery's non-standard one.

var arr=[0,1,2].map(function(n){
    return [ n, n + 1 ];
});

For unsupported browsers, you can use the compatibility patch from MDN.

Upvotes: 2

Guilherme Torres Castro
Guilherme Torres Castro

Reputation: 15350

$.map( [0,1,2], function(n){
   return n + 4;
 });

result: [4, 5, 6] 

$.map( [0,1,2], function(n){
   return [ n, n + 1 ];
 });

result : [0, 1, 1, 2, 2, 3]

You can check the diference in the return

Upvotes: 0

Šime Vidas
Šime Vidas

Reputation: 185933

$.map flattens the returned array:

A returned array will be flattened into the resulting array.

Source: http://api.jquery.com/jQuery.map/

Upvotes: 4

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