function hex_to_ascii(str1)  
 {  
    var hex  = str1.toString();  
    var str = '';  
    for (var n = 0; n < hex.length; n += 2) {  
        str += String.fromCharCode(parseInt(hex.substr(n, 2), 16));  
    }  
    return str;  
 }  
console.log(hex_to_ascii('3132'));  
console.log(hex_to_ascii('313030'));