Javascript equivalent to python's .format()

Question

I would like a javascript function that mimics the python .format() function that works like

.format(*args, **kwargs)

A previous question gives a possible (but not complete) solution for '.format(*args)

JavaScript equivalent to printf/string.format

I would like to be able to do

"hello {} and {}".format("you", "bob"
==> hello you and bob

"hello {0} and {1}".format("you", "bob")
==> hello you and bob

"hello {0} and {1} and {a}".format("you", "bob",a="mary")
==> hello you and bob and mary

"hello {0} and {1} and {a} and {2}".format("you", "bob","jill",a="mary")
==> hello you and bob and mary and jill

I realize that's a tall order, but maybe somewhere out there is a complete (or at least partial) solution that includes keyword arguments as well.

Oh, and I hear AJAX and JQuery possibly have methods for this, but I would like to be able to do it without all that overhead.

In particular, I would like to be able to use it with a script for a google doc.

Thanks

Answer 1

UPDATE: If you're using ES6, template strings work very similarly to String.format : https://developers.google.com/web/updates/2015/01/ES6-Template-Strings

If not, the below works for all the cases above, with a very similar syntax to python's String.format method. Test cases below.

 String.prototype.format = function() { var args = arguments; this.unkeyed_index = 0; return this.replace(/\\{(\\w*)\\}/g, function(match, key) { if (key === '') { key = this.unkeyed_index; this.unkeyed_index++ } if (key == +key) { return args[key] !== 'undefined' ? args[key] : match; } else { for (var i = 0; i < args.length; i++) { if (typeof args[i] === 'object' && typeof args[i][key] !== 'undefined') { return args[i][key]; } } return match; } }.bind(this)); }; // Run some tests $('#tests') .append( "hello {} and {}<br />".format("you", "bob") ) .append( "hello {0} and {1}<br />".format("you", "bob") ) .append( "hello {0} and {1} and {a}<br />".format("you", "bob", {a:"mary"}) ) .append( "hello {0} and {1} and {a} and {2}<br />".format("you", "bob", "jill", {a:"mary"}) ); 

 <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> <div id="tests"></div> 

Answer 2

This should work similar to python's format but with an object with named keys, it could be numbers as well.

String.prototype.format = function( params ) {
  return this.replace(
    /\{(\w+)\}/g, 
    function( a,b ) { return params[ b ]; }
  );
};

console.log( "hello {a} and {b}.".format( { a: 'foo', b: 'baz' } ) );
//^= "hello foo and baz."