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

• Stilltorik: In this particular case, the easiest thing to do would be to simply take a substring of your output string, to remove the '&'.
• John Dvorak: If you're using jQuery, let that to jQuery. Don't compose the URL yourself
• Amberlamps: If it is for transmitting parameters and this is the final query string, just leave the & at the end. It won´t matter.
• mplungjan: string += "&"+subkey + "="+ obj[key][subkey]; and at the end do ... string.substring(1)
• Menno: 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)?

Answer 1

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('&'));

Answer 2

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("&");
}

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

Answer 3

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

• mplungjan: Or string += "&"+subkey + "="+ obj[key][subkey]; and at the end ... string.substring(1)
• Grijesh Chauhan: @Christoph sorry I commented correct but answered wrong, for mplungjan let me think
• Grijesh Chauhan: @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: Yes it will, and I moved the & to the start.

Answer 4

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];
 }
}