Finding last iteration in for in loop javascript

Question

I am having following sample code

   var obj = { a: {b:1, c:3 }, d :{f:5}}
        var string = "";
        for(var key in obj){
            for(var subkey in obj[key]){
             string += subkey + "="+ obj[key][subkey] + "&";
             //for last iteration "&" should not be added.
         }
    }
   console.log(string);

output is

b=1&c=3&f=5&

Required Output

b=1&c=3&f=5

In this particular case, the easiest thing to do would be to simply take a substring of your output string, to remove the '&'. — Stilltorik
– Stilltorik, Commented May 22, 2013 at 9:49
If you're using jQuery, let that to jQuery. Don't compose the URL yourself — John Dvorak
– John Dvorak, Commented May 22, 2013 at 9:49
If it is for transmitting parameters and this is the final query string, just leave the & at the end. It won´t matter. — Amberlamps
– Amberlamps, Commented May 22, 2013 at 9:50
string += "&"+subkey + "="+ obj[key][subkey]; and at the end do ... string.substring(1) — mplungjan
– mplungjan, Commented May 22, 2013 at 9:52
Not a contribution to the question but to your case: are you sure your subkeys are unique (e.g. if subkey b in key a there cannot be a subkey b in key d)? — Menno
– Menno, Commented May 22, 2013 at 9:59

Rob Johnstone · Accepted Answer · 2013-05-22 09:55:43Z

9

An alternative approach would be:

var obj = { a: {b:1, c:3 }, d :{f:5}},
  array = [];
for(var key in obj){
  for(var subkey in obj[key]){
    array.push(subkey + "="+ obj[key][subkey]);
  }
}
console.log(array.join('&'));

answered May 22, 2013 at 9:55

Rob Johnstone

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Comments

Community · Accepted Answer · 2017-05-23 12:34:39Z

4

If you're creating the query-part of a url, I'd go with the solution provided here: How to create query parameters in Javascript?

If not, just drop the encoding-part :)

Copy of relevant code:

// Usage:
//   var data = { 'first name': 'George', 'last name': 'Jetson', 'age': 110 };
//   var querystring = EncodeQueryData(data);
// 
function EncodeQueryData(data)
{
   var ret = [];
   for (var d in data)
      ret.push(encodeURIComponent(d) + "=" + encodeURIComponent(data[d]));
   return ret.join("&");
}

edited May 23, 2017 at 12:34

CommunityBot

11 silver badge

answered May 22, 2013 at 9:57

SimonSimCity

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1 Comment

mplungjan Over a year ago

You should be able to drop the first encodeURIComponent I should think, unless the field names have non-ascii chars

Grijesh Chauhan · Accepted Answer · 2013-05-22 09:51:16Z

2

after for loop you can do like: string = string.slice(0,-1)

answered May 22, 2013 at 9:51

Grijesh Chauhan

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4 Comments

mplungjan Over a year ago

Or string += "&"+subkey + "="+ obj[key][subkey]; and at the end ... string.substring(1)

Grijesh Chauhan Over a year ago

@Christoph sorry I commented correct but answered wrong, for mplungjan let me think

Grijesh Chauhan Over a year ago

@mplungjan sorry :( I didn't understand, string.substring(1) will remove first char if I am not wrong, please example bit more I am also new learner web-languages ..

mplungjan Over a year ago

Yes it will, and I moved the & to the start.

letiagoalves · Accepted Answer · 2013-05-22 09:56:25Z

1

For each iterarion append first & except for the first one.

var obj = { a: {b:1, c:3 }, d :{f:5}}
var string = "";
for(var key in obj){
   for(var subkey in obj[key]){
      if(string !== "") string += "&";
      string += subkey + "=" + obj[key][subkey];
    }
}

edited May 22, 2013 at 9:56

answered May 22, 2013 at 9:50

letiagoalves

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