personally, I feel like a library is frequently (but not always) overkill when all you want is variable substitution

supplant.js

String.prototype.supplant = function (o) {
      o = o || {};
      return this.replace(/{([^{}]*)}/g, function(bracketed, clean){
      var object_value = o[clean];
      return ['string', 'number'].indexOf((typeof object_value)) > -1 ? object_value : bracketed;
  })
}

//example
var text = "{name} is feeling {feeling}".supplant({
	name: "Rob",
	feeling: "Good"
})