Why does javascript map function return undefined?

Question

My code

 var arr = [\'a\',\'b\',1];
 var results = arr.map(function(item){
                if(typeof item ===\'string\'){return item;}  
               });
<         


        

Answer 1

You only return a value if the current element is a string. Perhaps assigning an empty string otherwise will suffice:

var arr = ['a','b',1];
var results = arr.map(function(item){
    return (typeof item ==='string') ? item : '';  
});

Of course, if you want to filter any non-string elements, you shouldn't use map(). Rather, you should look into using the filter() function.