在多維數組中爲節點賦值javascript

Question

我想用一些新值（文本/對象/數組）來分配json對象內的元素。我有一個swap函數，它接受json對象，一個帶索引的數組來檢索元素和值來替換它。目前我正在使用eval，它符合一些是「邪惡」的。有沒有更好的方法來做到這一點，沒有評估或在這種情況下評估是好的？請記住它必須是動態的，因爲數組可能會改變。此外，注意到我正在編程創建數組參數可能很重要。

//array looks like: ["cluster", "2", "segment", "0", "node", "3"]  
JsonManager.prototype.swap = function(json, array, val){ 
     var statement = "json"; 
     for (var i = 0; i < array.length; i++) { 
      if(!isNumeric(array[i])) 
      { 
      statement += "[\"" + array[i] + "\"]";   
      }else{ 
       statement += "[" + array[i] + "]" 
      } 
     } 
     statement += " = val"; 
     eval(statement); 
    }; 

示例JSON對象：

var customers = { 
    "cluster": [{ 
     "clusterid": "cluster1.1", 
     "color": "blue", 
     "flights": "784", 
     "profit": "524125", 
     "clv": "2364", 
     "segment": [{ 
      "segmentid": "segment1.1", 
      "color": "green", 
      "flights": "82", 
      "profit": "22150", 
      "clv": "1564", 
      "node": [{ 
       "nodeid": "node1.1", 
       "color": "orange", 
       "xpos": "1", 
       "ypos": "1" 
      }, { 
       "nodeid": "node1.2", 
       "color": "blue", 
       "xpos": "1", 
       "ypos": "2" 
      }, { 
       "nodeid": "node1.3", 
       "color": "orange", 
       "xpos": "1", 
       "ypos": "3" 
      }, { 
       "nodeid": "node1.4", 
       "color": "orange", 
       "xpos": "1", 
       "ypos": "4" 
      }] 
     }, { 
      "segmentid": "segment1.2", 
      "color": "red", 
      "flights": "2", 
      "profit": "2150", 
      "clv": "1564", 
      "node": [{ 
       "nodeid": "node2.1", 
       "color": "tan", 
       "xpos": "2", 
       "ypos": "1" 
      }, { 
       "nodeid": "node2.2", 
       "color": "tan", 
       "xpos": "2", 
       "ypos": "2" 
      }, { 
       "nodeid": "node2.3", 
       "color": "tan", 
       "xpos": "2", 
       "ypos": "3" 
      }, { 
       "nodeid": "node2.4", 
       "color": "tan", 
       "xpos": "2", 
       "ypos": "4" 
      }] 
     }] 
    }, { 
     "clusterid": "cluster1.2", 
     "flights": "4", 
     "profit": "5245", 
     "clv": "2364", 
     "segment": [{ 
      "segmentid": "segment1.2", 
      "flights": "2", 
      "profit": "2150", 
      "clv": "1564", 
      "node": [{ 
       "nodeid": "node3.1", 
       "xpos": "3", 
       "ypos": "1" 
      }, { 
       "nodeid": "node3.2", 
       "xpos": "3", 
       "ypos": "2" 
      }, { 
       "nodeid": "node3.3", 
       "xpos": "3", 
       "ypos": "3" 
      }, { 
       "nodeid": "node3.4", 
       "xpos": "3", 
       "ypos": "4" 
      }] 
     }] 
    }, { 
     "clusterid": "cluster1.3", 
     "flights": "10", 
     "profit": "456978", 
     "clv": "548", 
     "segment": [{ 
      "segmentid": "segment1.3", 
      "flights": "2", 
      "profit": "2150", 
      "clv": "1564", 
      "node": [{ 
       "nodeid": "node4.1", 
       "xpos": "4", 
       "ypos": "1" 
      }, { 
       "nodeid": "node4.2", 
       "xpos": "4", 
       "ypos": "2" 
      }, { 
       "nodeid": "node4.3", 
       "xpos": "4", 
       "ypos": "3" 
      }, { 
       "nodeid": "node4.4", 
       "xpos": "4", 
       "ypos": "7" 
      }] 
     }] 
    }] 
}; 

這裏是我的測試方法：在這裏

JsonManager.prototype.init = function(){ 
    var clause = new Clause("nodeid", "node4.4"); 
    var indexes = this.search(customers, clause); 
    this.swap(customers, indexes.reverse(), {"name": "kevin"}); 
    var test = customers["cluster"][2]["segment"][0]["node"][3]; //hard coded pointer to node4.4 
    var breakPoint = "breakpoint"; //Just used as a point to stop the debugger to see test 
}; 

以供將來參考是進一步評論的解決方案：

JsonManager.prototype.swap = function(obj, path, value) { 

    //This is the inner function we are recursing into 
    function descend(obj, path) { 
    /*This if statement is used to stop the recrusion, 
    when we have iterated through all the paths, it returns 
    the object above our desired object */ 
     if (path.length == 0) { 
      return obj; 
     } 
    /*Recurse into the function passing in the top level object and remove 
    the top level object from our path*/ 
     return descend(obj[path[0]], path.slice(1)); 
    } 
//Pass in the object and the (path - the last element) 
    var node = descend(obj, path.slice(0, -1)); 
//Get the last node in path, pull it from node and assign the value 
    node[path[path.length - 1]] = value; 
}; 

Answer 1

你「 JSON「對象只是一個JavaScript對象。更重要的是，它是一棵樹，使用遞歸樹最容易遍歷。

JsonManager.prototype.swap = function(obj, path, value) { 
    function descend(obj, path) { 
     if (path.length == 0) { 
      return obj; 
     } 
     return descend(obj[path[0]], path.slice(1)); 
    } 

    var node = descend(obj, path.slice(0, -1)); 
    node[path[path.length - 1]] = value; 
}; 

slice將從數組中取出塊。所以path.slice(1)返回path沒有第一個元素，和path.slice(0, -1)返回它沒有最後一個。這意味着我們descend到倒數第二個節點的對象，然後使用普通數組表示法設置最後一個節點。讓你頭腦清醒的最簡單方法是用紙張上的手動工作，例如上面的例子。

Answer 2

沒有理由使用eval爲，只是對象分配給一個變量，並使用該變量踏入每個級別：

JsonManager.prototype.swap = function(json, array, val){ 
    var j = json; 
    for (var i = 0; i < array.length - 1; i++) { 
    j = j[array[i]]; 
    } 
    j[array[array.length - 1]] = val; 
};