String.Format in javascript?

Question

Hi

this is driving me nuts. I believe I asked this exact same question but I can't find it anymore(I used stackoverflow search, google search, manually searched my posts, searched my code).

I wanted something that would be like the C# String.Format where you could do something like

string format = String.Format("Hi {0}",name);

just for javascript of course and one person gave me a simple answer it was not like a jquery plugin or anything but I think you made some json thing or something and it worked and was simple to use.

I for the life of me can't find this post.

I do have this in my code but I can't seem to find anything that uses it and I am pretty sure I used it a couple times.

String.prototype.format = function(o)
{
    return this.replace(/{([^{}]*)}/g,
       function(a, b)
       {
           var r = o[b];
           return typeof r === 'string' ? r : a;
       }
    );
};

Answer 1

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 2

you can do something like

function format(str)
{
    for(i = 1; i < arguments.length; i++)
    {
        str = str.replace(‘{‘ + (i – 1) + ‘}’, arguments[i]);
    }
     return str;
}

Answer 3

Adapt the code from MsAjax string.

Just remove all of the _validateParams code and you are most of the way to a full fledged .net string class in javascript.

Okay, I liberated the msajax string class, removing all the msajax dependencies. Works great, just like .net string class, including trim functions and endsWith/startsWith etc.

P.S. - I left all of the Visual Studio JavaScript intellisense helpers and XmlDocs in place. They are innocuous if you don't use visual studio but you can remove them if you like.

<script src="script/string.js" type="text/javascript"></script>
<script type="text/javascript">
    var a = String.format("Hello {0}!", "world");
    alert(a);

</script>

String.js

// String.js - liberated from MicrosoftAjax.js on 03/28/10 by Sky Sanders 

/*
    Copyright (c) 2009, CodePlex Foundation
    All rights reserved.

    Redistribution and use in source and binary forms, with or without modification, are permitted 
    provided that the following conditions are met:

    *   Redistributions of source code must retain the above copyright notice, this list of conditions 
        and the following disclaimer.

    *   Redistributions in binary form must reproduce the above copyright notice, this list of conditions 
        and the following disclaimer in the documentation and/or other materials provided with the distribution.

    *   Neither the name of CodePlex Foundation nor the names of its contributors may be used to endorse or 
        promote products derived from this software without specific prior written permission.

    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS AS IS AND ANY EXPRESS OR IMPLIED 
    WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 
    A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE 
    FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 
    LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 
    INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 
    OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN 
    IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.</textarea>
*/

(function(window) {

    $type = String;
    $type.__typeName = 'String';
    $type.__class = true;

    $prototype = $type.prototype;
    $prototype.endsWith = function String$endsWith(suffix) {
        /// <summary>Determines whether the end of this instance matches the specified string.</summary>
        /// <param name="suffix" type="String">A string to compare to.</param>
        /// <returns type="Boolean">true if suffix matches the end of this instance; otherwise, false.</returns>
        return (this.substr(this.length - suffix.length) === suffix);
    }

    $prototype.startsWith = function String$startsWith(prefix) {
        /// <summary >Determines whether the beginning of this instance matches the specified string.</summary>
        /// <param name="prefix" type="String">The String to compare.</param>
        /// <returns type="Boolean">true if prefix matches the beginning of this string; otherwise, false.</returns>
        return (this.substr(0, prefix.length) === prefix);
    }

    $prototype.trim = function String$trim() {
        /// <summary >Removes all leading and trailing white-space characters from the current String object.</summary>
        /// <returns type="String">The string that remains after all white-space characters are removed from the start and end of the current String object.</returns>
        return this.replace(/^\s+|\s+$/g, '');
    }

    $prototype.trimEnd = function String$trimEnd() {
        /// <summary >Removes all trailing white spaces from the current String object.</summary>
        /// <returns type="String">The string that remains after all white-space characters are removed from the end of the current String object.</returns>
        return this.replace(/\s+$/, '');
    }

    $prototype.trimStart = function String$trimStart() {
        /// <summary >Removes all leading white spaces from the current String object.</summary>
        /// <returns type="String">The string that remains after all white-space characters are removed from the start of the current String object.</returns>
        return this.replace(/^\s+/, '');
    }

    $type.format = function String$format(format, args) {
        /// <summary>Replaces the format items in a specified String with the text equivalents of the values of   corresponding object instances. The invariant culture will be used to format dates and numbers.</summary>
        /// <param name="format" type="String">A format string.</param>
        /// <param name="args" parameterArray="true" mayBeNull="true">The objects to format.</param>
        /// <returns type="String">A copy of format in which the format items have been replaced by the   string equivalent of the corresponding instances of object arguments.</returns>
        return String._toFormattedString(false, arguments);
    }

    $type._toFormattedString = function String$_toFormattedString(useLocale, args) {
        var result = '';
        var format = args[0];

        for (var i = 0; ; ) {
            // Find the next opening or closing brace
            var open = format.indexOf('{', i);
            var close = format.indexOf('}', i);
            if ((open < 0) && (close < 0)) {
                // Not found: copy the end of the string and break
                result += format.slice(i);
                break;
            }
            if ((close > 0) && ((close < open) || (open < 0))) {

                if (format.charAt(close + 1) !== '}') {
                    throw new Error('format stringFormatBraceMismatch');
                }

                result += format.slice(i, close + 1);
                i = close + 2;
                continue;
            }

            // Copy the string before the brace
            result += format.slice(i, open);
            i = open + 1;

            // Check for double braces (which display as one and are not arguments)
            if (format.charAt(i) === '{') {
                result += '{';
                i++;
                continue;
            }

            if (close < 0) throw new Error('format stringFormatBraceMismatch');


            // Find the closing brace

            // Get the string between the braces, and split it around the ':' (if any)
            var brace = format.substring(i, close);
            var colonIndex = brace.indexOf(':');
            var argNumber = parseInt((colonIndex < 0) ? brace : brace.substring(0, colonIndex), 10) + 1;

            if (isNaN(argNumber)) throw new Error('format stringFormatInvalid');

            var argFormat = (colonIndex < 0) ? '' : brace.substring(colonIndex + 1);

            var arg = args[argNumber];
            if (typeof (arg) === "undefined" || arg === null) {
                arg = '';
            }

            // If it has a toFormattedString method, call it.  Otherwise, call toString()
            if (arg.toFormattedString) {
                result += arg.toFormattedString(argFormat);
            }
            else if (useLocale && arg.localeFormat) {
                result += arg.localeFormat(argFormat);
            }
            else if (arg.format) {
                result += arg.format(argFormat);
            }
            else
                result += arg.toString();

            i = close + 1;
        }

        return result;
    }

})(window);

Answer 4

Also Microsoft.Ajax has this function as well

Answer 5

Aside from the fact that you are modifying the String prototype, there is nothing wrong with the function you provided. The way you would use it is this way:

"Hello {0},".format(["Bob"]);

If you wanted it as a stand-alone function, you could alter it slightly to this:

function format(string, object) {
    return string.replace(/{([^{}]*)}/g,
       function(match, group_match)
       {
           var data = object[group_match];
           return typeof data === 'string' ? data : match;
       }
    );
}

Vittore's method is also good; his function is called with each additional formating option being passed in as an argument, while yours expects an object.

What this actually looks like is John Resig's micro-templating engine.

Answer 6

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 7

Here is what I use. I have this function defined in a utility file:

  String.format = function() {
      var s = arguments[0];
      for (var i = 0; i < arguments.length - 1; i++) {       
          var reg = new RegExp("\\{" + i + "\\}", "gm");             
          s = s.replace(reg, arguments[i + 1]);
      }
      return s;
  }

And I call it like so:

var greeting = String.format("Hi, {0}", name);

I do not recall where I found this, but it has been very useful to me. I like it because the syntax is the same as the C# version.