我正在嘗試在JavaScript中添加三個數字的和，但這給了我NaN。 為什么？

Question

我想從用戶那里收集三個數字，並使用函數和循環將它們相加。 我不斷提出NaN。 為什么是這樣？ 我嘗試將字符串提示轉換為Number對象以解決此問題。

 var userEntry1 = Number(window.prompt("Enter in a number of your choice")); var userEntry2 = Number(window.prompt("Enter in a number of your choice")); var userEntry3 = Number(window.prompt("Enter in a number of your choice")); var sum; var i; function addNumb(userEntry1, userEntry2, userEntry3) { "use strict"; sum = userEntry1 + userEntry2 + userEntry3; for (i = 1; i <= arguments.length; i += 1) { sum += Number(arguments[i]); } return sum; } addNumb(userEntry1, userEntry2, userEntry3); window.console.log(sum); 

Answer 1

在循環中，循環的長度等於arguments的長度，但是由於它是一個基於0的數組，因此您將進行一次迭代。 將<=更改為< ：

 var userEntry1 = Number(window.prompt("Enter in a number of your choice")); var userEntry2 = Number(window.prompt("Enter in a number of your choice")); var userEntry3 = Number(window.prompt("Enter in a number of your choice")); var sum; var i; function addNumb(userEntry1, userEntry2, userEntry3) { "use strict"; sum = userEntry1 + userEntry2 + userEntry3; for (i = 0; i < arguments.length; i += 1) { sum += Number(arguments[i]); } return sum; } addNumb(userEntry1, userEntry2, userEntry3); window.console.log(sum); 

Answer 2

arguments對象的鍵從0 ，因此您應從0到該對象循環到keys.length - 1 。

對象arguments實際上是一個key-value的對象，所以你可以使用運營商in 。

 var userEntry1 = Number(window.prompt("Enter in a number of your choice")), userEntry2 = Number(window.prompt("Enter in a number of your choice")), userEntry3 = Number(window.prompt("Enter in a number of your choice")), sum, i; function addNumb(userEntry1, userEntry2, userEntry3) { console.log(arguments)// keys from zero to keys.length - 1 "use strict"; sum = userEntry1 + userEntry2 + userEntry3; for (var arg in arguments) sum += Number(arguments[arg]); return sum; } addNumb(userEntry1, userEntry2, userEntry3); console.log(sum); 

Answer 3

您已經在對三個輸入的數字求和（ sum = userEntry1 + userEntry2 + userEntry3; ），並且根本不需要for循環。 如果必須使用for循環，則應刪除sum = userEntry1 + userEntry2 + userEntry3; 線。 使用"use strict" ，然后必須刪除函數參數聲明，以避免“聲明變量但未使用”錯誤。

 var userEntry1 = Number(window.prompt("Enter in a number of your choice")); var userEntry2 = Number(window.prompt("Enter in a number of your choice")); var userEntry3 = Number(window.prompt("Enter in a number of your choice")); function addNumb(userEntry1, userEntry2, userEntry3) { "use strict"; var sum = userEntry1 + userEntry2 + userEntry3; return sum; } function addNumb2() { "use strict"; for (var i = 0, sum = 0; i < arguments.length; i++) { sum += Number(arguments[i]); } return sum; } console.log(addNumb(userEntry1, userEntry2, userEntry3)); console.log(addNumb2(userEntry1, userEntry2, userEntry3));