如何將兩個數組組合爲笛卡爾積？

Question

我

array1 = [1,2,3,4,5]; 
array2 = ["one","two","three","four","five"]; 

我想array3其中與第一（和其他人）的array2元素等的array1所有元素

例如：

array3 = ["one 1", "two 1", "three 1", "four 1", "five 1", "one 2", "two 2", "three 2", "four 2", "five 2"...] 

我明白我需要使用循環，但我不知道該怎麼做。

Answer 1

您可以使用兩個for循環：

var array1 = [1,2,3,4,5]; 
var array2 = ["one","two","three","four","five"]; 

var array3 = []; 
for (var i = 0; i < array1.length; i++) { 
    for (var j = 0; j < array2.length; j++) { 
     array3.push(array2[j] + ' ' + array1[i]); 
    } 
} 

console.log(array3); 

Answer 2

可以使用Array.prototype.forEach()的迭代陣列上。

forEach()方法爲每個數組元素執行一次提供的函數。

var array1 = [1, 2, 3, 4, 5], 
 
    array2 = ["one", "two", "three", "four", "five"], 
 
    result = []; 
 

 
array1.forEach(function (a) { 
 
    array2.forEach(function (b) { 
 
     result.push(b + ' ' + a); 
 
    }); 
 
}); 
 

 
document.write('<pre>' + JSON.stringify(result, 0, 4) + '</pre>');

Answer 3

然而，隨着reduce和map和concat

摘錄另一種基於@Nina Scholz

var array1 = [1, 2, 3, 4, 5], 
 
    array2 = ["one", "two", "three", "four", "five"]; 
 

 
var result = array1.reduce(function (acc, cur) { 
 
    return acc.concat(array2.map(function (name) { 
 
     return name + ' ' + cur; 
 
    })); 
 
},[]); 
 

 
document.write('<pre>' + JSON.stringify(result, 0, 4) + '</pre>');

Answer 4

還有與循環選項：

var array2 = [1,2,3,4,5], 
array1 = ["one","two","three","four","five"], 
m = []; 
for(var a1 in array1){ 
    for(var a2 in array2){ 
     m.push(array1[a1]+ array2[a2]);  
    } 
} 
console.log(m); 

Answer 5

嘗試（JS）

function myFunction(){ 
      var F = [1, 2, 3, 4,5]; 
      var S = ["one", "two", "three", "four", "five"]; 
      var Result = []; 

      var k=0; 
      for (var i = 0; i < F.length; i++) { 
       for (var j = 0; j < S.length; j++) { 
        Result[k++] = S[j] + " " + F[i]; 
       } 
      } 

      console.log(Result); 
     } 

Answer 6

時array1.length和array2.length都是平等的，您可以使用此方法。

var array1 = [1, 2, 3, 4, 5]; 
 
var array2 = ["one", "two", "three", "four", "five"]; 
 
var length = array1.length; 
 
var array3 = new Array(Math.pow(length, 2)).fill(0).map((v, i) => array2[i % length] + ' ' + array1[i/length << 0]); 
 

 

 
document.body.textContent = JSON.stringify(array3);