getTime()方法怎么在javascript中使用

這期內容當中小編將會給大家帶來有關getTime()方法怎么在javascript中使用，文章內容豐富且以專業的角度為大家分析和敘述，閱讀完這篇文章希望大家可以有所收獲。

JavaScript有什么特點

1、js屬于一種解釋性腳本語言；2、在絕大多數瀏覽器的支持下，js可以在多種平臺下運行，擁有著跨平臺特性；3、js屬于一種弱類型腳本語言，對使用的數據類型未做出嚴格的要求，能夠進行類型轉換，簡單又容易上手；4、js語言安全性高，只能通過瀏覽器實現信息瀏覽或動態交互，從而有效地防止數據的丟失；5、基于對象的腳本語言，js不僅可以創建對象，也能使用現有的對象。

1、理解getTime

getTime() 方法返回一個時間的格林威治時間數值。

可以使用這個方法把一個日期時間賦值給另一個Date 對象。

語法：

dateObj.getTime()
參數：

無。

返回值：

getTime 方法的返回值一個數值，表示從1970年1月1日0時0分0秒（UTC，即協調世界時）距離該日期對象所代表時間的毫秒數。

例子：

使用 getTime() 復制日期對象

創建一個擁有相同時間值的日期對象。

var birthday = new Date(1994, 12, 10);
var copy = new Date();
copy.setTime(birthday.getTime());

測試結果如下：

    既然表示從1970年1月1日開始計算的毫秒數，如果小于1970年呢，會是什么情況？（測試結果如下，是負數）

2、應用場景

2.1 測量代碼執行時間

連續調用兩個新生成的日期對象的 getTime 方法，根據兩次調用的返回值求得時間差。這可以用于計算某些操作的執行時間。

var end, start, i;
start = new Date();
for (i = 0; i < 100000; i++) {
 Math.sqrt(i);
}
end = new Date();

console.log("Operation took " + (end.getTime() - start.getTime()) + " msec");

在chrome瀏覽器中進行測試：

2.2 甘特圖時間表示

最近在調整teamwork gantt中，發現，是一個task任務項的開始時間與結束時間，都是用一個整數表示，而該數值就是UTC表示法。格式如下：

{"tasks":[
   {"id":-1,"name":"Gantt editor","code":"","level":0,"status":"STATUS_ACTIVE","canWrite":true,"start":1396994400000,"duration":21,"end":1399672799999,"startIsMilestone":true,"endIsMilestone":false,"collapsed":false,"assigs":[],"hasChild":true}
   ,{"id":-2,"name":"coding","code":"","level":1,"status":"STATUS_ACTIVE","canWrite":true,"start":1396994400000,"duration":10,"end":1398203999999,"startIsMilestone":false,"endIsMilestone":false,"collapsed":false,"assigs":[],"description":"","progress":0,"hasChild":true}
   ,{"id":-3,"name":"gantt part","code":"","level":2,"status":"STATUS_ACTIVE","canWrite":true,"start":1396994400000,"duration":2,"end":1397167199999,"startIsMilestone":false,"endIsMilestone":false,"collapsed":false,"assigs":[],"depends":"","hasChild":false}
   ,{"id":-4,"name":"editor part","code":"","level":2,"status":"STATUS_SUSPENDED","canWrite":true,"start":1397167200000,"duration":4,"end":1397685599999,"startIsMilestone":false,"endIsMilestone":false,"collapsed":false,"assigs":[],"depends":"","hasChild":false}
   ,{"id":-5,"name":"testing","code":"","level":1,"status":"STATUS_SUSPENDED","canWrite":true,"start":1398981600000,"duration":6,"end":1399672799999,"startIsMilestone":false,"endIsMilestone":false,"collapsed":false,"assigs":[],"depends":"","description":"","progress":0,"hasChild":true}
   ,{"id":-6,"name":"test on safari","code":"","level":2,"status":"STATUS_SUSPENDED","canWrite":true,"start":1398981600000,"duration":2,"end":1399327199999,"startIsMilestone":false,"endIsMilestone":false,"collapsed":false,"assigs":[],"depends":"8SF:11","hasChild":false}
   ,{"id":-7,"name":"test on safari","code":"","level":2,"status":"STATUS_SUSPENDED","canWrite":true,"start":1398981600000,"duration":2,"end":1399327199999,"startIsMilestone":false,"endIsMilestone":false,"collapsed":false,"assigs":[],"depends":"8SF","hasChild":false}
   ,{"id":-8,"name":"test on ie","code":"","level":2,"status":"STATUS_SUSPENDED","canWrite":true,"start":1400688000000,"duration":3,"end":1400947199999,"startIsMilestone":false,"endIsMilestone":false,"collapsed":false,"assigs":[],"depends":"","hasChild":false}
   ,{"id":-9,"name":"test on chrome","code":"","level":2,"status":"STATUS_SUSPENDED","canWrite":true,"start":1399327200000,"duration":2,"end":1399499999999,"startIsMilestone":false,"endIsMilestone":false,"collapsed":false,"assigs":[],"links":"","hasChild":false}
   ,{"id":-10,"name":"Gantt editor","code":"","level":0,"status":"STATUS_ACTIVE","canWrite":true,"start":1396994400000,"duration":21,"end":1399672799999,"startIsMilestone":true,"endIsMilestone":false,"collapsed":false,"assigs":[],"hasChild":true}
   ,{"id":-11,"name":"coding","code":"","level":1,"status":"STATUS_ACTIVE","canWrite":true,"start":1396994400000,"duration":10,"end":1398203999999,"startIsMilestone":false,"endIsMilestone":false,"collapsed":false,"assigs":[],"description":"","progress":0,"hasChild":true}
   ,{"id":-12,"name":"gantt part","code":"","level":2,"status":"STATUS_ACTIVE","canWrite":true,"start":1396994400000,"duration":2,"end":1397167199999,"startIsMilestone":false,"endIsMilestone":false,"collapsed":false,"assigs":[],"depends":"","hasChild":false}
   ,{"id":-14,"name":"editor part","code":"","level":2,"status":"STATUS_SUSPENDED","canWrite":true,"start":1397167200000,"duration":4,"end":1397685599999,"startIsMilestone":false,"endIsMilestone":false,"collapsed":false,"assigs":[],"depends":"","hasChild":false}
   ,{"id":-15,"name":"testing","code":"","level":1,"status":"STATUS_SUSPENDED","canWrite":true,"start":1398981600000,"duration":6,"end":1399672799999,"startIsMilestone":false,"endIsMilestone":false,"collapsed":false,"assigs":[],"depends":"","description":"","progress":0,"hasChild":true}
   ,{"id":-16,"name":"test on safari","code":"","level":2,"status":"STATUS_SUSPENDED","canWrite":true,"start":1398981600000,"duration":2,"end":1399327199999,"startIsMilestone":false,"endIsMilestone":false,"collapsed":false,"assigs":[],"depends":"","hasChild":false}
   ,{"id":-17,"name":"test on ie","code":"","level":2,"status":"STATUS_SUSPENDED","canWrite":true,"start":1399327200000,"duration":3,"end":1399586399999,"startIsMilestone":false,"endIsMilestone":false,"collapsed":false,"assigs":[],"depends":"","hasChild":false}
   ,{"id":-18,"name":"test on chrome","code":"","level":2,"status":"STATUS_SUSPENDED","canWrite":true,"start":1399327200000,"duration":2,"end":1399499999999,"startIsMilestone":false,"endIsMilestone":false,"collapsed":false,"assigs":[],"depends":"","hasChild":false}
   ],"selectedRow":0,"canWrite":true,"canWriteOnParent":true}

在甘特圖中，使用getTime表示時間有以下優勢：

計算兩個時間差比較方便
數據存儲結構比較簡單
由于gantt涉及到畫圖，使用整型數據方便處理

3、瀏覽器的兼容性

使用js要收到瀏覽器的限制，不同瀏覽器對js類庫的支持強弱也不同。而作為標準類庫Date的一個方法，其適應的瀏覽器如下：

上述就是小編為大家分享的getTime()方法怎么在javascript中使用了，如果剛好有類似的疑惑，不妨參照上述分析進行理解。如果想知道更多相關知識，歡迎關注億速云行業資訊頻道。