如何加倍數組中的其他元素？

Question

我需要在程序結束時輸出兩個數組。

第一個數組是用戶輸入的內容。第二個數組應複製第一個元素，並用其double元素替換每個其他元素。假設用戶將「1,2,3,4,5」保存到第一個陣列。第二個陣列應具有：「1,,3,,5」。

這是我到目前爲止。

頭標籤

function toDouble(modArray) 
{ 
    var modified = new Array(); 
    for(var i = 1; i < modArray.length; i+=2) 
    { 
     modified.push(modArray[i] * 2); 
    } 
return modified; 
} 

---

BODY標籤

var origArray = new Array(); 
var modArray = new Array(); 
while() //ignore the while loop part; it is working fine 
{ 
    origArray = parseInt(prompt("Enter a number: ")); 
    document.write(origArray); //output 1 
    modArray.push(origArray); 
} 
var modified = toDouble(modArray); 
document.write(modified); //output 2 

我僅接收一倍號碼，而不是整個陣列。例如，如果我輸入「1，2，3，4，5」，我只能得到「4，8」作爲輸出。

我該如何解決這個問題？先謝謝你！

Answer 1

另一種解決方案考慮原陣列

只備用元素像這樣做： -

function toDouble(modArray) { 
    for (var i = 1; i < modArray.length; i+=2) { 
     modArray[i] *= 2; 
    } 
    return modArray; 
} 

Answer 2

你只需要對你的代碼的一些變化：

function toDouble(modArray) { 
 
    var modified = modArray.slice(0); // copy the whole `modArray` 
 
    for(var i = 1; i < modified.length; i+=2) { 
 
     modified[i] *= 2; // replace the value at `i`, for every other number. 
 
    } 
 
    return modified; 
 
} 
 

 
var a = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10], 
 
    b = toDouble(a); 
 

 
alert(JSON.stringify(b));

Answer 3

function toDouble(modArray) 
{ 
    var modified = new Array(); 
    for(var i = 1; i < modArray.length; i+=2) 
    { 
     modified.push(modArray[i-1]); 
     modified.push(modArray[i] * 2); 
    } 

    if(modified.length < modArray.length) 
     modified.push(modArray[modArray.length - 1]); 
    return modified; 
} 

Answer 4

function toDouble(modArray) { 
    var modified = new Array(); 
    for (var i = 0; i < modArray.length; i++) { 
     if (i % 2 == 0) 
      modified.push(modArray[i]); 
     else 
      modified.push(modArray[i] * 2); 
    } 
    return modified; 
} 

例子：

var a = [1, 2, 3, 4, 5] 

toDouble(a); // output: [1, 4, 3, 8, 5] 

Answer 5

前面已經解釋過這個問題什麼時候要創建新的數組您使用Array.map()

function toDouble(modArray) { 
 
    return modArray.map(function(val, i) { 
 
    return i % 2 == 0 ? val : val * 2; 
 
    }) 
 
} 
 

 

 
var modArray = new Array(), 
 
    origArray; 
 
while (modArray.length < 5) //ignore the while loop part; it is working fine 
 
{ 
 
    origArray = parseInt(prompt("Enter a number: ")); 
 
    modArray.push(origArray); 
 
} 
 

 
snippet.log('modArray: ' + modArray) 
 
var modified = toDouble(modArray); 
 
snippet.log('Result: ' + modified)

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