---
robots: noindex, nofollow
tags: refactoring
---

# Preserve Whole Object

> 練習用的 [REPL](https://repl.it/@yaosiang/PreserveWholeObject)

const low = aRoom.daysTempRange.low;
const high = aRoom.daysTempRange.high;
if (!aPlan.withinRange(low, high))
    alerts.push("room temperature went outside range");

class HeatingPlan {
    withinRange(bottom, top) {
        return (bottom >= this._temperatureRange.low) && (top <= this._temperatureRange.high);
    }
}

建立一個新 function，但名稱可以亂取。

class HeatingPlan {
    withinRange(bottom, top) {
        return (bottom >= this._temperatureRange.low) && (top <= this._temperatureRange.high);
    }
    // 建立一個新 function，但運算邏輯委派給原有 function
    xxNEWwithinRange(aNumberRange) {
        return this.withinRange(aNumberRange.low, aNumberRange.high);
    }
}

const low = aRoom.daysTempRange.low;
const high = aRoom.daysTempRange.high;
if (!aPlan.xxNEWwithinRange(aRoom.daysTempRange))
    alerts.push("room temperature went outside range");

class HeatingPlan {
    // withinRange(bottom, top) {
    //     return (bottom >= this._temperatureRange.low) && (top <= this._temperatureRange.high);
    // }
    
    // 把運算邏輯搬回新的 function
    xxNEWwithinRange(aNumberRange) {
        return (aNumberRange.low >= this._temperatureRange.low) &&
        (aNumberRange.high <= this._temperatureRange.high);
    }
}

把新 function 名稱改成原本的名字。

if (!aPlan.withinRange(aRoom.daysTempRange))
    alerts.push("room temperature went outside range");

class HeatingPlan {
    withinRange(aNumberRange) {
        return (aNumberRange.low >= this._temperatureRange.low) &&
        (aNumberRange.high <= this._temperatureRange.high);
    }
}