如何在Javascript中將4個位置的項目向上移動

Question

如何將項目數組向上移動4個位置？

我有以下字符串數組：

var array1 = ["t0","t1","t2","t3","t4","t5"]; 

我需要一個功能轉換 「陣列1」 導致：提前

// Note how "t0" moves to the fourth position for example 
var array2 = ["t3","t4","t5","t0","t1","t2"]; 

感謝。

Answer 1

array1 = array1.concat(array1.splice(0,3)); 

運行在Firebug以下驗證

var array1 = ["t0","t1","t2","t3","t4","t5"]; 
console.log(array1); 
array1 = array1.concat(array1.splice(0,3)); 
console.log(array1); 

導致

["t0", "t1", "t2", "t3", "t4", "t5"] 
["t3", "t4", "t5", "t0", "t1", "t2"] 

Answer 2

可以slice的數組，然後join它以顛倒的次序：

var array2 = array1.slice(3).concat(array1.slice(0, 3)); 

Answer 3

還有一個辦法是這樣的：

var array2 = array1.slice(0); 

for (var i = 0; i < 3; i++) { 
    array2.push(array2.shift()); 
} 

Answer 4

function shiftArray(theArray, times) { 
    // roll over when longer than length 
    times = times % theArray.length; 
    var newArray = theArray.slice(times); 
    newArray = newArray.concat(theArray.slice(0, times)); 
    return newArray; 
} 

var array1 = ["t0","t1","t2","t3","t4","t5"]; 
var array2 = shiftArray(array1, 3); 
alert(array2); // ["t3","t4","t5","t0","t1","t2"] 

Answer 5

另一種方法 - 將以下代碼粘貼到大螢火蟲控制檯，以確認它的工作原理：

var a = [0, 1, 2, 3, 4, 5]; 
for (var i = 0; i < 3; i++) { 
    a.unshift(a.pop()); 
} 
// the next line is to show it in the Firebug console; variable "a" holds the array 
a.toString(",");