Comparison between 2 strings in javascript is not working

Question

I wrote this code example to know the index position of an element that has a specific value in "Name". My variable data contains a list of those elements.

var data = {"Attributes":[
    {"Name":"bedrooms","Value":"4"},
    {"Name":"bathrooms","Value":"2"},
    {"Name":"property_type","Value":"House"},
    {"Name":"rateable_value","Value":"$780,000"},
    {"Name":"price","Value":"Price by negotiation"},
    {"Name":"location","Value":"13"},
    {"Name":"district","Value":"Queenstown-Lakes"},
    {"Name":"suburb","Value":"Lower Shotover"},
    {"Name":"region","Value":"Otago"},
    {"Name":"floor_area","Value":"254m²"},
    {"Name":"land_area","Value":"1690m²"},
    {"Name":"property_id","Value":"CBM959"},
    {"Name":"in_the_area","Value":"playground"},
    {"Name":"parking","Value":"Large double garage"}
]}

find_index = function(list, str){
        list.each(function(index, value){
            console.log("Comparing "+value.Name+" with "+str);
            if(value.Name == str){
                return index;
            }
        });
    };

console.log(find_index($(data.Attributes), "bedrooms"))

When I execute this code, it prints in the log all the comparisons and then return "undefined". What I was expecting is to stop iterations when comparison succeeded, and return 0, which is the position of the element with name "bedrooms".

What is happening here? and how can I solve it?

Your return statement returns from the internal, anonymous function, not the find_index function. — Barmar
– Barmar, Commented Nov 15, 2013 at 18:52

PSL · Accepted Answer · 2013-11-15 19:06:41Z

You need to return the value from your function.

Try

find_index = function(list, str){
    var idx;
        list.each(function(index, value){
            console.log("Comparing "+value.Name+" with "+str);
            if(value.Name === str){
                idx = index;
                return false; //Exit out of the loop after the match
            }
        });
    return idx;
 };

Return value in .each loop is used as a boolean value to exit or continue the loop.

Also you don't need to create a jquery object, you can just use $.each on arrays as is like this:

find_index = function(list, str){
        var idx;
            $.each(list, function(index, value){
                 if(value.Name === str){
                    idx = index;
                    return false; //Exit out of the loop after the match
                }
            });
        return idx;
     };
console.log(find_index(data.Attributes, "bedrooms"));

You can infact simplify this much better to, especially if you want to get multiple matches. But there is no way to break out of map though:

find_index = function(list, str){
  return $.map(list, function(val, idx){
       if(val.Name === str) return idx;
   })[0]; //for multiple matches remove 0
};

console.log(find_index(data.Attributes, "district"));

user1769790 · Accepted Answer · 2013-11-15 19:08:49Z

1

Incase, the string comparison is failing try using localeCompare; this comes into rescue to match strings exactly.

find_index = function(list, str){
var localIndex;
    list.each(function(index, value){
        console.log("Comparing "+value.Name+" with "+str + index);
        if(str.localeCompare(value.Name) == 0)
        {

            localIndex = index;
            return false;
        }

    });
    return localIndex;
};

console.log(find_index($(data.Attributes), "bedrooms"));

answered Nov 15, 2013 at 19:08

user1769790

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Comments

Jake · Accepted Answer · 2013-11-15 18:51:40Z

0

The each function won't stop (break) unless you return false. You could have a variable you assign the matching index to and then return false.

answered Nov 15, 2013 at 18:51

Jake

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