myCoolObject {
  a: 0
  b: 12
  c: 24
}

I want to concatenate a, b and c so that they look like a unique string "a-b-c" (or "0-12-24" in the example).

a, b and c will always represent numbers. Converting each one of them from int to string require a lot of code: I'd just use sprintf() if I were in PHP or C, but how can I do this in JS without using toString() for each parameter and writing too much code?

Whole code:

var pickedDate = this.getSelectedDay().year.toString() + "-" + this.getSelectedDay().month.toString() + this.getSelectedDay().day.toString();

Seriously? Isn't there any more efficient way of doing this in js?

myCoolObject {
  a: 0
  b: 12
  c: 24
}

I want to concatenate a, b and c so that they look like a unique string "a-b-c" (or "0-12-24" in the example).

a, b and c will always represent numbers. Converting each one of them from int to string require a lot of code: I'd just use sprintf() if I were in PHP or C, but how can I do this in JS without using toString() for each parameter and writing too much code?

Whole code:

var pickedDate = this.getSelectedDay().year.toString() + "-" + this.getSelectedDay().month.toString() + this.getSelectedDay().day.toString();

Seriously? Isn't there any more efficient way of doing this in js?

• javascript
• string-concatenation

• Will the properties always be a, b and c or is there an arbitrary number of properties in each object? – Mike Christensen Commented Jun 6, 2013 at 15:15
• nope, same data structure all the times. – Saturnix Commented Jun 6, 2013 at 15:15
• Yea, I think what you have is probably the best way. You can perhaps create a toString prototype on whatever object holds this data. – Mike Christensen Commented Jun 6, 2013 at 15:17

5 Answers 5

var myCoolString = myCoolObject.a + '-' + myCoolObject.b + '-' + myCoolObject.c;

EDIT:

With ES6, you can use template strings to interpolate numbers into strings:

let myCoolString = `${myCoolObject.a}-${myCoolObject.b}-${myCoolObject.c}`;

Try it:

var myCoolObject = {
  a: 0,
  b: 12,
  c: 24
};

var myCoolString = myCoolObject.a + '-' + myCoolObject.b + '-' + myCoolObject.c;

console.log(typeof myCoolString);
console.log(myCoolString);

how can I do this in JS without [...] writing too much code?

If you know all of your numbers are positive, you can write even less code to achieve the same as we know JavaScript executes left-to-right.

var obj = {a: 0, b: 12, c: 24}; /* define object
String + Number = String
                  String + Number = String
                                    String + Number = String
String + Number + Number + Number     = String    */
  ''   +  obj.a + -obj.b + -obj.c; // = "0-12-24"

The - were inserted because String + -Number = "String-Number", e.g.

'AK' + -47 // "AK-47"

Without much code it looks perfect here is the demo

myObj = {
  a: 0,
  b: 12,
  c: 24
}; 

var r="";

// iterate through all object properties
for (var p in myObj) 
{
    //concatenate it
    r+=myObj[p]+"-";
}

//remove the last dash
r=r.substring(0,r.length-1);

alert(r.substring(0,r.length-1));

This is mostly done with Array.join:

var pickedDate = [
    this.getSelectedDay().year, 
    this.getSelectedDay().month, 
    this.getSelectedDay().day
].join("-")

Although I personally prefer a small utility function similar to pythonic format():

format = function(fmt /*, args */) {
    var args = [].slice.call(arguments, 1);
    return fmt.replace(/{(\d+)}/g, function($0, $1) { 
        return String(args[$1])
    })
}

and then:

var pickedDate = format('{0}-{1}-{2}', 
    this.getSelectedDay().year, 
    this.getSelectedDay().month, 
    this.getSelectedDay().day)

1. Try sprintf() for JavaScript.

2. Add new method to string

   if (!String.prototype.format) {
   String.prototype.format = function() {
      var args = arguments;
      return this.replace(/{(\d+)}/g, function(match, number) { 
         return typeof args[number] != 'undefined'
          ? args[number]
           : match
         ;
      });
     };
   }
   
   "{0} - {1} - {2}".format(myCoolObject.a, myCoolObject.b,myCoolObject.c)