jquery 解析json

1.

 var str=\'{ "name": "John" }\';
    var obj = eval(\'(\' + str + \')\'); 
    alert( obj.name);

    var str2="{ \'name\': \'John\' }";
    var obj2 = eval(\'(\' + str2 + \')\'); 
    alert( obj2.name);

    var str3="{ name: \'John\' }";
    var obj3 = eval(\'(\' + str3 + \')\'); 
    alert( obj3.name);

2.

  var str=\'{ "name": "John" }\';
    var obj = jQuery.parseJSON(str)
    alert("1"+ obj.name);

3.

 var str = \'{ "name": "mady", "age": "24" }\';
        var obj = JSON.parse(str);
        alert(obj.name);