Javascript Map 返回未定义，尽管(键，值)对已定义

Question

我正在使用 nodejs 在 Linux 终端中运行此代码片段。尽管(键，值)对设置正确，但代码打印未定义。对于这个问题有什么解释或解决方法吗？

function trial() {
    var obj1 = {};
    var obj2 = {};
    obj1.fund = 1;
    obj1.target = 2;
    obj2.fund = 1;
    obj2.target = 2;
    states = [];
    states.push(obj1);
    states.push(obj2);
    actions = [1,2,3,4];
    table = new Map();
    for (var state of states) {
        for (var action of actions) {
            cell = {};
            cell.state = state;
            cell.action = action;
            table.set(cell, 0);
        }
    }
    var obj = {};
    obj.state = states[1];
    obj.action = actions[1];
    console.log(table.get(obj));   
}

Answer 1

您需要原始对象引用来匹配表(Map())中的键，让我们保存每个新的单元格，它是每个对象引用来显示这一点。

即使你有对象的深度克隆，对于 Map() 来说，它也不是相同的键。

     var obj1 = {};
     var obj2 = {};
     obj1.fund = 1;
     obj1.target = 2;
     obj2.fund = 1;
     obj2.target = 2;
     states = [];
     states.push(obj1);
     states.push(obj2);
     actions = [1,2,3,4];
     table = new Map();
     var objRefs = [];
     var count = 0;
     for (var state of states) {
         for (var action of actions) {
             cell = {};
             cell.state = state;
             cell.action = action;
             table.set(cell, count);
             objRefs.push(cell);  //hold the object reference
             count ++;
         }
     }
     
     for (var i = 0; i < objRefs.length; i++) {
       console.log(table.get(objRefs[i]));
     }

     // Copy by reference
     var pointerToSecondObj = objRefs[1]; 
     
     console.log(table.get(pointerToSecondObj));
     
     //Deep clone the object
     var deepCloneSecondObj =  JSON.parse(JSON.stringify(objRefs[1]));
 
     console.log(table.get(deepCloneSecondObj));