如何降低 Javascript 中 if else 語句的復雜性？

Question

我有以下場景，其中有多個 if else 條件。

以下代碼的圈復雜度顯示為 7。

是否有更好的方法來使用 Javascript 編寫以下代碼片段以降低代碼的復雜性？

function setTime() {

var currentTime = "3/4/2020, 2:53:42 PM"
var selectedTime = "3/5/2020, 2:53:42 PM"

if( Date.parse(currentTime) < Date.parse(selectedTime)) {
    callThisMethod('Current time less than selected time');
} else if (Date.parse(currentTime) > Date.parse(selectedTime)) {
    callThisMethod('Current time Greater than selected time');
} else {
    callThisMethod('Current time is equal to selected time');
}
}

function callThisMethod(message) {
 console.log(message);
}

setTime();

Answer 1

可能的選項之一：

const currentTime = new Date("3/4/2020, 2:53:42 PM"),
      selectedTime = new Date("3/5/2020, 2:53:42 PM")

callThisMethod(`Current time is ${currentTime < selectedTime ? 'less than' : currentTime > selectedTime ? 'greater than' : 'equal to'} selected time`)

Answer 2

您可以先獲取 ISO 日期，然后比較這些日期。

 function setTime() { var currentTime = "3/4/2020, 2:53:42 PM", selectedTime = "3/5/2020, 2:53:42 PM", current = new Date(currentTime).toISOString(), selected = new Date(selectedTime).toISOString(); if (current < selected) { callThisMethod('Current time less than selected time'); } else if (current > selected) { callThisMethod('Current time Greater than selected time'); } else { callThisMethod('Current time is equal to selected time'); } } function callThisMethod(message) { console.log(message); } setTime();

Answer 3

function setTime() {

    var currentTime = "3/4/2020, 2:53:42 PM";
    var selectedTime = "3/5/2020, 2:53:42 PM";
    let a = new Date(currentTime).getTime();
    let b = new Date(selectedTime).getTime();
    let str = ['less than','is equal','greater than'];
    let n = (a-b)/Math.abs(a-b) || 0;

    callThisMethod(`Current time ${str[n]} selected time`);
}

function callThisMethod(message) {
 console.log(message);
}

setTime();

根據https://jshint.com/ ，此函數的圈復雜度數為 2。

Answer 4

也許您應該編寫“以減少代碼”或“編寫更好的代碼”。 這個 if 或 else if 語句並不復雜。

實際上，為什么不從 if/else if 中 console.log 消息，並且避免調用另一個函數？

function setTime() {
      var currentTime = "3/4/2020, 2:53:42 PM",
          selectedTime = "3/5/2020, 2:53:42 PM",
          current = new Date(currentTime).toISOString(),
          selected =  new Date(selectedTime).toISOString();

      if (current < selected) {
        console.log('Current time less than selected time');
      } else if (current > selected) {
        console.log('Current time Greater than selected time')
      } else {
        console.log('Current time is equal to selected time');
      }
    }

    setTime();

Answer 5

這種方法可能有幾種可能的答案。 您可以做的一件事是保持條件不受評估。 因此，與其在條件表達式中解析日期，不如在比較之前解析它。 之后，您可以將最常見的條件，您認為可能經常出現的情況作為第一個條件，並使用二分搜索方法打破其他條件。 考慮以下代碼片段：

function setTime() {
    var currentTime = Date.parse("3/4/2020, 2:53:42 PM")
    var selectedTime = Date.parse("3/5/2020, 2:53:42 PM")
    if(currentTime < selectedTime) {
       callThisMethod('Current time less than selected time');
    } else {
       if (currentTime > selectedTime) {
         callThisMethod('Current time Greater than selected time');
       } else {
          callThisMethod('Current time is equal to selected time');
         }
      }
}

function callThisMethod(message) {
 console.log(message);
}

setTime();

請注意如何使用拆分技術將條件分解為多個部分。 或者您可以使用 switch case 而不是條件。 與 if-else 條件相比，已發現 switch case 在后續條件上花費的增量成本更少。 考慮以下片段：

function setTime() {
        var currentTime = Date.parse("3/4/2020, 2:53:42 PM")
        var selectedTime = Date.parse("3/5/2020, 2:53:42 PM")
        switch(true){
            case (currentTime > selectedTime):
                callThisMethod('Current time Greater than selected time');
                break;
            case (currentTime < selectedTime):
                callThisMethod('Current time less than selected time')
                break;
            default:
                 callThisMethod('Current time is equal to selected time')    
}
    }

    function callThisMethod(message) {
     console.log(message);
    }

    setTime();