var tpl = '<li>${name}</li><li>${age}</li>';
var reg = /\${([A-Za-z0-9_]+)}/g;
var data = [{"name": "小明","age": "6"},{"name": "小明明","age": "66"}];
var ret= ['<ul>'];
for(var i = 0,len = data.length;i < len;++i){
    ret.push(tpl.replace(reg,function(){
        return data[i][arguments[1]];
    }));
}
ret.push('</ul>');
ret = ret.join('');
console.log(ret);

这个主要考你正则了吧

t = t.replace(/\$\{([a-z]+)\}/g,function(){
    return data[0][arguments[1]]
})

function foo(data){
    var result="";
    for(var i=0;i<data.length;i++)
        result+="<ul><li>"+data[i]['name']+"</li><li>"+data[i]["age"]+"</li></ul>";
    return result;
}

正则该是

var reg = /\$\{([^{}]+)\}/g;