JScript 的變量 · javascript詳解

| JScript? | [逄晟統蕉](#) | |-----|-----| # JScript 腔曹講 ?睡晤最逄晟笢ㄛ蚚珨輸杅擂講趙珨跺衙癩﹝ ~~~ How old am I? ~~~ 婓 Jscript 笢ㄛ曹講岆跤衙癩腔靡備˙坳測桶賸跤堤侘潔腔硉﹝絞妏蚚蜆曹講奀ㄛ妗暱岆蚚腔坳垀測桶腔杅擂﹝跤堤尨瞰ㄩ ~~~ NumberOfDaysLeft = EndDate 每 TodaysDate; ~~~ 儂迮腔燴賤岆妏蚚曹講懂湔揣﹜腕善甜紱釬褐掛笢堤珋腔垀衄腔祥骯硉﹝斐膘衄砩砱腔曹講靡備˙晞衾梗?燴賤褐掛﹝ ### 曹講汒隴曹講婓褐掛笢腔菴珨棒堤珋岆婓汒隴笢﹝曹講婓菴珨棒蚚善奀憩扢離衾囀湔笢ㄛ晞衾綴懂婓褐掛笢竘蚚﹝妏蚚曹講眳?珂輛俴汒隴﹝褫眕妏蚚 **var** 壽瑩趼懂輛俴曹講汒隴﹝ ~~~ var count; // ~~~ 等跺汒隴﹝ ~~~ var count, amount, level; // ~~~ 蚚等跺 ~~~ var ~~~ 壽瑩趼汒隴腔嗣跺汒隴﹝ ~~~ var count = 0, amount = 100; // ~~~ 珨沭逄曆笢腔曹講汒隴睿場宎趙﹝ ?彆婓 **var **逄曆笢羶衄場宎趙曹講ㄛ曹講赻雄? JScript 硉 **undefined**﹝鴃奪甜祥假?ㄛ筍汒隴逄曆笢綺謹 **var** 壽瑩趼岆磁楊腔 JScript 逄楊﹝涴奀ㄛJScript 賤庋?跤軑曹講?擁毓峓腔褫獗僅﹝絞婓徹最撰笢汒隴珨跺曹講奀ㄛ坳祥夔蚚衾?擁毓峓˙涴笱?錶狟ㄛ曹講汒隴斛剕蚚 **var** 壽瑩趼﹝ ### 曹講韜靡曹講靡備岆珨跺梓妎睫﹝Jscript 笢ㄛ蚚梓妎睫懂ㄩ - 韜靡曹講ㄛ - 韜靡滲杅ㄛ - 跤堤悜遠腔梓?﹝ JScript 岆珨笱?煦湮苤迡腔逄晟﹝秪森曹講靡備 *myCounter *睿曹講靡備 *mYCounter* 岆祥珨欴腔﹝曹講腔靡備褫眕岆?砩酗僅﹝斐膘磁楊腔曹講靡備茼郩悜?狟寞寀ㄩ - 菴珨跺趼睫斛剕岆珨跺 ASCII 趼譫ㄗ湮苤迡歙褫ㄘㄛ麼珨跺狟赫盄(_)﹝蛁砩菴珨跺趼睫祥夔岆杅趼﹝ - 綴哿腔趼睫斛剕岆趼譫﹜杅趼麼狟赫盄﹝ - 曹講靡備珨隅祥夔岆 [悵隱趼](#)﹝ 狟醱跤堤磁楊曹講靡備腔珨虳尨瞰ㄩ ~~~ _pagecount Part9 Number_Items ~~~ 狟醱跤堤拸虴曹講靡備腔珨虳尨瞰ㄩ ~~~ 99Balloons // ~~~ 祥夔眕杅趼羲芛﹝ ~~~ Smith&Wesson // ~~~ ※迵§睫瘍ㄗ ~~~ & ~~~ ㄘ趼睫蚚衾曹講靡備岆拸虴腔﹝ 絞猁汒隴珨跺曹講甜輛俴場宎趙ㄛ筍衱祥砑硌隅?睡杻忷硉ㄛ褫眕董硉峈 JScript 硉 [null](#)﹝狟醱跤堤尨瞰﹝ ~~~ var bestAge = null; var muchTooOld = 3 * bestAge; // muchTooOld ~~~ 腔硉峈 ~~~ 0 ~~~ ﹝ ?彆汒隴賸珨跺曹講筍羶衄勤?董硉ㄛ蜆曹講湔婓ㄛ?硉峈Jscript 硉 [undefined](#)﹝狟醱跤堤尨瞰﹝ ~~~ var currentCount; var finalCount = 1 * currentCount; // finalCount ~~~ 腔硉峈 ~~~ NaN ~~~ ㄛ秪峈 ~~~ currentCount ~~~ 峈 ~~~ undefined ~~~ ﹝ 蛁砩婓 JScript 笢 **null** 睿 **undefined** 腔翋猁?梗岆 **null** 腔紱釬砓杅趼 0ㄛ奧 **undefined** 腔紱釬砓杻忷硉**NaN** ㄗ祥岆珨跺杅趼ㄘ﹝勤 **null** 硉睿 **undefined** 硉釬掀誕軞岆眈脹腔﹝ 褫眕祥蚚 **var **壽瑩趼汒隴曹講ㄛ甜董硉﹝涴憩岆笐宒汒隴﹝ ~~~ noStringAtAll = ""; // ~~~ 笐宒汒隴曹講 ~~~ noStringAtAll ~~~ ﹝ 祥夔妏蚚帤冪徹汒隴腔曹講﹝ ~~~ var volume = length * width; // ~~~ 渣昫 ~~~ ~~~ 〞 ~~~ length ~~~ 睿 ~~~ width ~~~ 甜祥湔婓﹝ ### ?秶蛌遙桶湛宒笢紱釬砐腔杅擂濬倰眈骯奀 JScript 賤庋?符夔勤??硉﹝?彆桶湛宒祥冪徹?秶蛌遙憩彸芞勤謗跺祥骯腔杅擂濬倰ㄗ?珨跺峈杅趼ㄛ鍚珨跺峈趼睫揹ㄘ硒俴堍呾ㄛ蔚莉汜渣昫賦彆﹝筍婓 Jscript 笢?錶憩祥骯賸﹝ JScript 岆珨笱赻蠶濬倰腔逄晟﹝坳腔曹講羶衄啎隅濬倰ㄗ眈勤衾?濬倰逄晟ㄛ? C++ㄘ﹝眈毀ㄛJScript 曹講腔濬倰眈茼衾坻蠅婦漪腔硉腔濬倰﹝涴笱紱釬腔疑揭岆夔蔚硉釬峈鍚珨濬倰揭燴﹝ 婓 Jscript 笢ㄛ褫眕勤祥骯濬倰腔硉硒俴堍呾ㄛ祥斛童陑 JScript 賤庋?莉汜祑都﹝眈毀ㄛJScript 賤庋?赻雄蔚杅擂濬倰眳珨蜊曹ㄗ?秶蛌遙ㄘ峈鍚珨笱杅擂濬倰ㄛ?綴硒俴堍呾﹝瞰?ㄩ | 堍呾 | 賦彆 | |-----|-----| | 杅硉迵趼睫揹眈樓 | 蔚杅硉?秶蛌遙峈趼睫揹﹝ | | 票嫌硉迵趼睫揹眈樓 | 蔚票嫌硉?秶蛌遙峈趼睫揹﹝ | | 杅硉迵票嫌硉眈樓 | 蔚票嫌硉?秶蛌遙峈杅硉﹝ | 蕉藉狟醱腔尨瞰﹝ ~~~ var x = 2000; // ~~~ 珨跺杅趼﹝ ~~~ var y = "Hello"; // ~~~ 珨跺趼睫揹﹝ ~~~ x = x + y; // ~~~ 蔚杅趼?秶蛌遙峈趼睫揹﹝ ~~~ document.write(x); // ~~~ 懷堤 ~~~ 2000Hello ~~~ ﹝ 猁砑珆宒華蔚趼睫揹蛌遙峈淕杅ㄛ妏蚚 [parseInt 源楊](#)﹝猁砑珆宒華蔚趼睫揹蛌遙峈杅趼ㄛ妏蚚 [parseFloat 源楊](#)﹝?蛁砩ㄛ掀誕湮苤奀趼睫揹赻雄蛌遙峈眈脹腔杅趼ㄛ筍樓楊ㄗ蟀諉ㄘ堍呾奀悵隱峈趼睫揹﹝ [? 2000 Microsoft Corporation 唳?垀衄﹝悵隱垀衄?瞳﹝妏蚚寞隅﹝](#)