javascript how to add a variable to a string

Question

I'm using javascript and jquery, I have a string like

  var apiUrlAnswer = 'https://api.stackexchange.com/2.0/answers/{ids}?order=desc&sort=activity&site=stackoverflow';

I need replace the {ids} with a variable.

In C# is possible to use a method called

String.Format(https://api.stackexchange.com/2.0/answers/{0}?order=desc&sort=activity&site=stackoverflow, myVariable);

I would like to know if exist something similar in Javascript so I can avoid simple string concatenation.

Thanks for your help!

nnnnnn · Accepted Answer · 2012-08-02 06:33:54Z

5

Use the String .replace() method:

var apiUrlAnswer = 'https://api.stackexchange.com/2.0/answers/{ids}?order=desc&sort=activity&site=stackoverflow';

apiUrlAnswer = apiUrlAnswer.replace("{ids}", yourVariable);

// OR, if there might be more than one instance of '{ids}' use a regex:
apiUrlAnswer = apiUrlAnswer.replace(/\{ids\}/g, yourVariable);

edited Aug 2, 2012 at 6:33

answered Aug 2, 2012 at 6:26

nnnnnn

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3 Comments

GibboK Over a year ago

Thanks nnnnnn.. do you know alternative day to do it?

nnnnnn Over a year ago

There are any number of ways to do it using whatever combination of JavaScript's String manipulation methods takes your fancy, but .replace() is an easy way to do it with one statement...

nnnnnn Over a year ago

P.S. There are some libraries that implement a String.format() type function, e.g., sprintf() for JavaScript. If you Google "JavaScript String.format" you'll get a bunch of options.

Chris Moutray · Accepted Answer · 2012-08-02 09:05:12Z

3

Well here's a String.format (like c#); I've extended javascripts String object to include a format method like this:

String.format = function(stringToFormat, argsForFormat) {

    for (var i = 0; i < argsForFormat.length; i++) {
        var regex = new RegExp('\{(' + i + ')}', 'g');
        stringToFormat = stringToFormat.replace(regex, argsForFormat[i]);
    }

    return stringToFormat;    
};

You can call it like this

var args = [1, 'activity', 'stackoverflow', 'desc']   
var apiUrlAnswer = 'https://api.stackexchange.com/2.0/answers/{0}?order={3}&sort={1}&site={2}';
var apiUrlAnswer = String.format(apiUrlAnswer, args);

Or an inline version would look like this

var apiUrlAnswer = String.format('https://api.stackexchange.com/2.0/answers/{0}?order={3}&sort={1}&site={2}', [1, 'activity', 'stackoverflow', 'desc']);

and another example

String.format("http://{0}.{1}.com", ['www', 'stackoverflow']);

edited Aug 2, 2012 at 9:05

answered Aug 2, 2012 at 6:47

Chris Moutray

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2 Comments

nnnnnn Over a year ago

+1. Nice. Or even better, replace(new RegExp('{'+i+'}', 'g'), ... so that it can replace multiple instances of {0}.

Chris Moutray Over a year ago

@nnnnnn amended as suggested but could only get it to work with a more complex pattern '\{(' + i + ')}'

Flash · Accepted Answer · 2012-08-02 06:36:38Z

1

If you are doing this frequently, a more robust alternative to using a regex is to use a client side templating engine like mustache.js. I have used this successfully and it's quick and lightweight.

var view = {
  ids: "Andrew"
};

var output = Mustache.render("https://api.stackexchange.com/2.0/answers/{{ids}}?order=desc&sort=activity&site=stackoverflow", view);

This has the advantage of separating your data and presentation nicely.

edited Aug 2, 2012 at 6:36

answered Aug 2, 2012 at 6:29

Flash

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Comments

Sune Trudslev · Accepted Answer · 2012-08-02 06:28:06Z

0

How about just using replace:

apiUrlAnswer = apiUrlAnswer.replace('{ids}', 'test');

answered Aug 2, 2012 at 6:28

Sune Trudslev

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Comments

Alfred · Accepted Answer · 2012-08-02 06:31:17Z

0

Try

var id = 'your_id';
var apiUrlAnswer = 'https://api.stackexchange.com/2.0/answers/'+id+'?order=desc&sort=activity&site=stackoverflow';

answered Aug 2, 2012 at 6:31

Alfred

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