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function?count(){

????//獲取第一個輸入框的值
????var?a=document.getElementById("txt1").value;
????//獲取第二個輸入框的值
????var?b=document.getElementById("txt2").value;
????//獲取選擇框的值
????//獲取通過下拉框來選擇的值來改變加減乘除的運算法則
????var?c=document.getElementById("select").value;
????switch(c){
????????case?'+':
????????????d=Number(a)+Number(b);
????????????break;
????????case?'-':
????????????d=a-b;
????????????break;
????????case?'*':
????????????d=a*b;
????????????break;
????????case?'/':
????????????d=a/b;
????????????break;
????}
????//設置結果輸入框的值
????var?d;
????document.getElementById("fruit").value=d;

}

慕用3695885

2019-02-14

源自：JavaScript進階篇 6-11

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qq_慕數據8341535
2019-02-16

?function count(){
??? //獲取第一個輸入框的值
??? var txt1 = document.getElementById("txt1").value;
??? //把txt1變成整型變量txt11
??? var txt11 = parseInt(txt1);
?? ?//獲取第二個輸入框的值
?? ?var txt2 = document.getElementById("txt2").value;
?? ?//把txt2變成整型變量txt22
?? ?var txt22 = parseInt(txt2);
?? ?//獲取選擇框的值
?? ?
?? ?//獲取通過下拉框來選擇的值來改變加減乘除的運算法則
?? ?var jg;? //定義存放結果的變量jg
?? ?var select = document.getElementById("select").value;
?? ?switch(select)
?? ?{
?? ???? case "+":
?? ???????? jg = txt11 + txt22;
?? ???????? break;
?? ???? case "-":
?? ???????? jg = txt11 - txt22;
?? ???????? break;
?? ???? case "*":
?? ???????? jg = txt11 * txt22;
?? ???????? break;
?? ???? case "/":
?? ???????? jg = txt11 / txt22;
?? ?}
??? //設置結果輸入框的值
??? var fruit = document.getElementById("fruit");
??? fruit.value = jg;? //把計算結果放入fruit文本框中
?? }