Concatenating numbers as string in Javascript

Question

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?

Will the properties always be a, b and c or is there an arbitrary number of properties in each object? — Mike Christensen, Jun 06 '13 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, Jun 06 '13 at 15:17

rink.attendant.6 · Accepted Answer · 2017-08-10T08:11:48.300

6

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);

edited Aug 10 '17 at 08:11

answered Jun 06 '13 at 15:14

rink.attendant.6

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they're numbers: wouldn't js try to sum them? – Saturnix Jun 06 '13 at 15:15
3

@Saturnix Because there's a string being concatenated in between. If you just wanted to concatenate them (without characters in between), you could just use `var str = "" + myCoolObject.a + myCoolObject.b + myCoolObject.c;`. As soon as a string is encountered, concatenation will happen, not addition. If addition is needed, parentheses can be used – Ian Jun 06 '13 at 15:15
I added a jsFiddle example to demonstrate. – rink.attendant.6 Jun 06 '13 at 15:18

Paul S. · Answer 2 · 2013-06-06T15:38:27.977

2

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"

edited Jun 06 '13 at 15:38

answered Jun 06 '13 at 15:20

Paul S.

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+1 I don't know why this has been downvoted - looks like a legit answer to me. – Saturnix Jun 06 '13 at 15:45
legit okay but how is anyone supposed to maintain this code? You save two quotation marks and one plus sign compared to rink's answer and in exchange readability takes a huge hit. – Joooeey Jan 31 '18 at 21:21

score 1 · Answer 3 · answered Jun 06 '13 at 15:17

1

Try sprintf() for JavaScript.

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)

answered Jun 06 '13 at 15:17

Igor S.

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1

Please link to the [original code](http://stackoverflow.com/a/4673436/989121) instead of copypasting it. – georg Jun 06 '13 at 15:34

georg · Answer 4 · 2013-06-06T15:31:23.437

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)

score 1 · Answer 5 · answered Jun 06 '13 at 15:27

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));

Concatenating numbers as string in Javascript

5 Answers5

Try it:

Linked

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