CODEWITHSUNDEEP
javascriptcoffeescript
Jeetendra
Jeetendra

Reputation: 205

Unwanted js code added while compiling coffeescript

I am new to coffeescript and I have a coffee script code as

getProviderListDisplayValues:(domainId) ->      
    displayValues = []
    $.ajax 
        contentType: 'application/json',
        url: "/Services/ListProviders?domainid=#{domainId}",
        success: (data) ->          
            for oneResponse in data
                displayValues.push oneResponse.name     
    displayValues

which is compiled to 

CounselorHome.prototype.getProviderListValues = function(domainId) {
   var values;
   values = [];
   $.ajax({
     contentType: 'application/json',
     url: "/Services/ListProviders?domainid=" + domainId,
     success: function(data) {
       var oneResponse, _i, _len, _results;
       _results = [];
       for (_i = 0, _len = data.length; _i < _len; _i++) {
         oneResponse = data[_i];
         _results.push(values.push(oneResponse.id));
       }
       return _results;
     }
   });
   return values;
};

I just want to push values to values[] & displayValues[] but why is the _results[] array created? Does it hampers the browser efficiency? Is there any way removing such unnessary code? May be, by editing my coffee script.

EDIT : WORKING CONDITION

But when I put an alerting code as

 $.ajax 
        contentType: 'application/json',
        url: "/Services/ListProviders?domainid=#{domainId}",
        success: (data) ->          
            for oneResponse in data
                displayValues.push oneResponse.name     
 alert displayValues
 displayValues

This code works and I can retrieve the required data.

Upvotes: 0

Views: 40

Answers (1)

Bergi
Bergi

Reputation: 664297

Apart from that your code wouldn't work anyway, the _results are generated because of coffeescripts implicit function return values - and loops are only expressions as well that generate arrays. The docs state:

Sometimes functions end with loops that are intended to run only for their side-effects. Be careful that you're not accidentally returning the results of the comprehension in these cases, by adding a meaningful return value — like true — or null, to the bottom of your function.

So the javascript that you expected can be created by writing

…
    success: (data) ->
        for oneResponse in data
            displayValues.push oneResponse.name
        return
…

("Trailing return and return undefined are now optimized away." - since version 1.0.1);
See also Is there any way to not return something using CoffeeScript?

However, what you actually want is this:

getProviderListDisplayValues:(domainId) ->
    $.ajax
        contentType: 'application/json',
        url: "/Services/ListProviders?domainid=#{domainId}"
    .then (data) ->          
        for oneResponse in data
            oneResponse.name

…

getProviderListDisplayValues(…).then (displayValues) ->
    …

Upvotes: 2

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