string_format.js

string_format.js

/*
 * {% ABC %}
 *
 */

function string_format(format, context) {
  if ((typeof format != "string") ||
      (typeof context != "object")) {
    return; 
  } 

  var result = [];
  var qs = 0;
  var init = 0;
  var tlen = format.length;
  var i = 0;

  while(i < tlen) { 
    if ((format[i] == "{") && (format[i+1] == "%")) {
      //tag start
      qs = 1;
      //valid tag location
      init = i + 2;
      //skip {
      i = i + 1;
      //ignore until qs 2
    }
    if ((format[i] == "%") && (format[i+1] == "}")) {
      qs = 2; 
      //close quote, fallthrough   
    } 

    if (qs == 0) {
      //normal character
      result.push(format[i]); 
    } else if (qs == 2) {
      //close quote, insert context 
      var tag = format.slice(init, i).trim(" "); 
      result.push(context[tag]);
      qs = 0; 
      //skip %
      i  = i + 1;
    } 
    //skip % or { or add index
    i =  i + 1;
  }
  return result.join("");
};