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
– Mike Christensen, 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
– Mike Christensen, Commented Jun 6, 2013 at 15:17

rink.attendant.6 · Accepted Answer · 2017-08-10 08:11:48Z

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, 2017 at 8:11

answered Jun 6, 2013 at 15:14

rink.attendant.6

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3 Comments

Saturnix Over a year ago

they're numbers: wouldn't js try to sum them?

Ian Over a year ago

@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

rink.attendant.6 Over a year ago

I added a jsFiddle example to demonstrate.

Paul S. · Accepted Answer · 2013-06-06 15:38:27Z

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 6, 2013 at 15:38

answered Jun 6, 2013 at 15:20

Paul S.

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2 Comments

Saturnix Over a year ago

+1 I don't know why this has been downvoted - looks like a legit answer to me.

Joooeey Over a year ago

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.

Nick · Accepted Answer · 2013-06-06 15:27:03Z

1

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));

answered Jun 6, 2013 at 15:27

Nick

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Comments

georg · Accepted Answer · 2013-06-06 15:31:23Z

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)

edited Jun 6, 2013 at 15:31

answered Jun 6, 2013 at 15:24

georg

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Comments

Igor S. · Accepted Answer · 2013-06-06 15:17:51Z

0

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 6, 2013 at 15:17

Igor S.

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1 Comment

georg Over a year ago

Please link to the original code instead of copypasting it.

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