工廠功能：為什么狀態變量不更改為“ OK”？

Question

我正在從javascript類切換到工廠功能。 除了參數，我還需要內部屬性，例如。 以下簡化示例中的狀態。 那么，為什么狀態沒有設置為OK，應該怎么做呢？

const Model = (name) => {
    name = "myname";
    let status = "initial";

    const setOK = () => {
        status = "OK";
    }
    return {name, status, setOK}
};

const m = Model();
console.log(m.status); //status is initial
m.setOK();
console.log(m.status);  //expecting OK, but still initial

Answer 1

當前，返回的對象永遠不會改變：您的

return {name, status, setOK}

返回具有這三個屬性的對象，其值與返回該對象時的值相同 。 如果要更改對象，請事先在Model內定義該對象，然后在setOK內setOK對象進行setOK ：

 const Model = (name) => { name = "myname"; let status = "initial"; const setOK = () => { obj.status = "OK"; }; const obj = { name, status, setOK }; return obj; }; const m = Model(); console.log(m.status); m.setOK(); console.log(m.status); 

Answer 2

對象組成

使用Object.assign()合並對象或“繼承”方法，而無需使用class或prototype 。 組成重於繼承

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演示

演示中詳細評論

 /* Object monitor has setOK() method. Note the parenthesis wrapped around the curly braces ensures that the object literal will be invoked as a expression. The props object from Model is passed to monitor object */ const monitor = props => ({ setOK: () => { props.status = "OK"; } }); /* Factory Function Note the object literal props. props will be passed through Object.assign() method in order to inherit the method setOK() from the monitor object. */ const Model = name => { let props = { name: name, status: "initial" }; return Object.assign(props, monitor(props)); }; // Create object m with the name: "checkStatus" const m = Model("checkStatus"); // Verify object m is named "checkStatus" console.log('name: '+m.name); // Check status console.log('status: '+m.status); // Invoke .setOK() method m.setOK(); // Check status console.log('status: '+m.status);