方法鏈接在javascript中失敗

Question

我正在嘗試訓練自己編寫鏈接功能，但出現錯誤

Cannot read property 'minus' of undefined(…)

我的代碼有什么問題？

 var math = function(){ var result = 0; var add = function(param){ result += param; }; var minus = function(param){ result -= param; }; var print = function(){ console.log(result) }; return {add:add, minus: minus, print:print}; } var calculator = math(); var result = calculator.add(5).minus(1).print(); console.log(result) 

Answer 1

在這種情況下，您需要將對象（ this ）返回到“鏈”中，就像您期望的那樣

您的print()也不會返回任何內容，因此result始終是不確定的。

 var math = function(){ var result = 0; var add = function(param){ result += param; return this; }; var minus = function(param){ result -= param; return this; }; var print = function(){ console.log('result: ' + result); // print doesnt return anything, it needs to if you want to assign anything by calling it return result; }; return {add:add, minus: minus, print:print}; } var calculator = math(); var result = calculator.add(5).minus(1).print(); console.log(result) 

Answer 2

您還可以存儲對返回對象的引用。

 var math = function() { var result = 0; var add = function(param) { result += param; return math; }; var minus = function(param) { result -= param; return math; }; var print = function() { console.log(result) }; var math = { add: add, minus: minus, print: print }; return math; } var calculator = math(); calculator.add(5).minus(1).print();