Simple template function to replace pattern in string with object properties or function returned value.

template.js

/**
 * Simple template function. 
 * 
 * For each pattern in argument template, it is replaced with actual property from argument data.
 *   t('{greeting} world', {greeting: 'hello'}) === 'hello world'
 *
 * Sequence of property in argument data doesn't matter:
 *   t('{g} {x}', {g: '{o}', o: 'x'})) === '{o} {x}'
 *   t('{g} {x}', {o: 'x', g: '{o}'})) === '{o} {x}'
 *
 * If matching pattern is function in property of argument data, the function is invoked with two arguments:
 * The matching pattern and the whole input string.
 *    t('{greeting} world', {greeting: function(key, str) { return 'hello ' + key; } }) === 'hello greeting world'
 *
 * @argument str template string
 * @argument data the actual data 
 */
function t(str, data){
    return str.replace(/\{([^\}]+?)\}/g, function(match, key) {
        return (key in data) 
            ? (typeof data[key] === 'function'? data[key](key, str) : data[key] )
            : match;
    });
}