Use of String.Format in JavaScript?

Question

This is driving me nuts. I believe I asked this exact same question, but I can\'t find it any more (I used Stack Overflow search, Google Search, manually searched my po

Answer 1

Here is an solution that allows both prototype and function options.

// --------------------------------------------------------------------
// Add prototype for 'String.format' which is c# equivalent
//
// String.format("{0} i{2}a night{1}", "This", "mare", "s ");
// "{0} i{2}a night{1}".format("This", "mare", "s ");
// --------------------------------------------------------------------

if(!String.format)
    String.format = function(){
        for (var i = 0, args = arguments; i < args.length - 1; i++)
            args[0] = args[0].replace("{" + i + "}", args[i + 1]);
        return args[0];
    };
if(!String.prototype.format && String.format)
    String.prototype.format = function(){
        var args = Array.prototype.slice.call(arguments).reverse();
        args.push(this);
        return String.format.apply(this, args.reverse())
    };

Enjoy.

Answer 2

Without a third party function:

string format = "Hi {0}".replace('{0}', name)

With multiple params:

string format = "Hi {0} {1}".replace('{0}', name).replace('{1}', lastname)

Answer 3

Use sprintf library

Here you have a link where you can find the features of this library.

Answer 4

String.Format method from .NET Framework has multiple signatures. The one I like the most uses params keyword in its prototype, i.e.:

public static string Format(
    string format,
    params Object[] args
)

Using this version, you can not only pass variable number of arguments to it but also an array argument.

Because I like the straightforward solution provided by Jeremy, I'd like to extend it a bit:

var StringHelpers = {
    format: function(format, args) {
        var i;
        if (args instanceof Array) {
            for (i = 0; i < args.length; i++) {
                format = format.replace(new RegExp('\\{' + i + '\\}', 'gm'), args[i]);
            }
            return format;
        }
        for (i = 0; i < arguments.length - 1; i++) {
            format = format.replace(new RegExp('\\{' + i + '\\}', 'gm'), arguments[i + 1]);
        }
        return format;
    }
};

Now you can use your JavaScript version of String.Format in the following manners:

StringHelpers.format("{0}{1}", "a", "b")

and

StringHelpers.format("{0}{1}", ["a", "b"])

Answer 5

Your function already takes a JSON object as a parameter:

string format = "Hi {foo}".replace({
    "foo": "bar",
    "fizz": "buzz"
});

if you notice, the code:

var r = o[b];

looks at your parameter (o) and uses a key-value-pairs within it to resolve the "replace"

Answer 6

String.prototype.format = function () {
    var formatted = this;
    for (var arg in arguments) {
        formatted = formatted.split('{' + arg + '}').join(arguments[arg]);
    }
    return formatted;
};

USAGE:

'Hello {0}!'.format('Word')                 ->     Hello World!

'He{0}{0}o World!'.format('l')            ->     Hello World!

'{0} {1}!'.format('Hello', 'Word')     ->     Hello World!

'{0}!'.format('Hello {1}', 'Word')     ->     Hello World!