JavaScript中的多维数组用法指南

多维数组未直接在JavaScript中提供。如果要使用任何充当多维数组的东西, 则需要使用另一个一维数组来创建多维数组。因此, JavaScript中的多维数组被称为另一个数组中的数组。我们需要将一些数组放入一个数组中, 然后整个事情就像多维数组一样工作。其他数组将插入其中的数组, 该数组在我们的代码中用作多维数组。定义多维数组与定义普通一维数组完全相同。

一维数组：

var arr = []; // Empty 1D array
var arr1 = ["A", "B", "C", "D"] // 1D array contains some alphabets
var arr1 = [1, 2, 3, 4, 5] // 1D array contains some digits

多维数组：

方法1：

1st, need to define some 1D array
var arr1 = ["ABC", 24, 18000];
var arr2 = ["EFG", 30, 30000];
var arr3 = ["IJK", 28, 41000];
var arr4 = ["EFG", 31, 28000];
var arr5 = ["EFG", 29, 35000];
// "salary" defines like a 1D array but it already contains some 1D array
var salary = [arr1, arr2, arr3, arr4, arr5];

这里arr1, arr2, …arr5是里面的一些一维数组薪水数组。

方法2：

var salary = [
   ["ABC", 24, 18000], ["EFG", 30, 30000], ["IJK", 28, 41000], ["EFG", 31, 28000], ];

这里, 薪水数组的工作方式类似于多维数组。这种表示法称为数组文字。

访问薪水数组的元素：

• 要访问数组元素, 我们需要一个基于索引的简单表示法

  // This notation access the salary of "ABC" person which is 18000, // [0] selects 1st row, and [2] selects the 3rd element
  // of that 1st row which is 18000
  salary[0][2];
  
  // Similarly, salary[3][2]; // Selects 28000
  
  **This notation is used for both Method 1 and Method 2.
  

• 对于许多迭代, 我们需要使用循环来访问元素,

  // This loop is for outer array
  for (var i = 0, l1 = salary.length; i < l1; i++) {
  
      // This loop is for inner-arrays
      for (var j = 0, l2 = salary[i].length; j < l2; j++) {
  
          // Accessing each elements of inner-array
          documents.write( salary[i][j] ); 
      }
  }

在多维数组中添加元素：多维数组中的元素添加可以通过以下两种方式实现：内部数组or外层阵列。内部数组可以通过两种不同的方式完成。

• 向内部数组添加元素：
  • 我们可以使用简单方括号在多维数组中添加元素的符号。

    salary[3][3] = "India";
    
    // It adds "India" at the 4th index of 4th sub-array, // If we print the entire 4th sub-array, document.write(salary[3]);
    // the output will be :  ["EFG", 31, 28000, "India"]
    // indexing starts from 0

  • 我们可以用推()在数组中添加元素的方法。

    salary[3].push("India", "Mumbai");
    
    // It add "India" at the 4th index and "Mumbai" at
    // 5th index of 4th sub-array
    // If we print the entire 4th sub-array, // document.write(salary[3]);
    // The output will be :  ["EFG", 31, 28000, "India", "Mumbai"]
    // Indexing starts from 0

• 向外部数组添加元素：它与以前的方法非常相似。

  salary.push(["MNO", 29, 33300]);
  // This row added after the last row in the "salary" array

删除多维数组中的元素：我们可以用pop()从内部数组中删除元素的方法, 也可以使用pop()删除整个内部数组的方法。

// Remove last element from 4th sub-array
// That is 28000 indexing starts from 0
salary[3].pop(); 

// Removes last sub-array
// That is "["EFG", 31, 28000]"
salary.pop();

范例1：

// Prints a simple multidimensional array in JavaScript
<script>
var arr1 = [ "ABC" , 24, 18000];
var arr2 = [ "EFG" , 30, 30000];
var arr3 = [ "IJK" , 28, 41000];
var arr4 = [ "EFG" , 31, 28000];
var arr5 = [ "EFG" , 29, 35000];
var salary = [arr1, arr2, arr3, arr4, arr5]; 
for ( var i = 0; i < salary.length; i++) {
     document.write(salary[i] + "<br>" );
}
</script>

输出如下：

ABC, 24, 18000
EFG, 30, 30000
IJK, 28, 41000
EFG, 31, 28000
EFG, 29, 35000

范例2：

// Prints a simple multidimensional array in
// JavaScript with different declaration
<script>
var salary = [
    [ "ABC" , 24, 18000], [ "EFG" , 30, 30000], [ "IJK" , 28, 41000], [ "EFG" , 31, 28000], ]; 
for ( var i = 0; i < salary.length; i++) {
     document.write(salary[i] + "<br>" );
}
</script>

输出如下：

ABC, 24, 18000
EFG, 30, 30000
IJK, 28, 41000
EFG, 31, 28000
EFG, 29, 35000

范例3：

// Prints a simple multidimensional array in JavaScript
// where we just print the salary of a specific person
<script>
var salary = [
    [ "ABC" , 24, 18000], [ "EFG" , 30, 30000], [ "IJK" , 28, 41000], [ "EFG" , 31, 28000], ]; 
document.write( "salary of 2nd person : " + salary[1][2] + "<br>" );
document.write( "salary of 4th person : " + salary[3][2] + "<br>" );
</script>

输出如下：

salary of 2nd person : 30000
salary of 4th person : 28000

范例4：

// Prints a simple multidimensional array in
// JavaScript where we add elements in the array 
// using simple square bracket and push() method
<script>
var salary = [
    [ "ABC" , 24, 18000], [ "EFG" , 30, 30000], [ "IJK" , 28, 41000], [ "EFG" , 31, 28000], ]; 
  
// Prints first array
document.write( "Original array :<br>" );
for ( var i = 0; i < salary.length; i++) {
     document.write(salary[i] + "<br>" );
}
  
// Adding "India" at the 4th index of 4th sub array
salary[3][3] = "India" ;
  
document.write( "<br>after adding \"India\" at the 4th array :<br>" );
for ( var i = 0; i < salary.length; i++) {
     document.write(salary[i] + "<br>" );
}
  
document.write( "<br>after adding \"USA\" and \"Canada\" "
      + "at the 3rd array using \"push()\" method :<br>" );
salary[2].push( "USA" , "Canada" );
  
// Adding "USA" and "Canada" in the 2nd sub-array
for ( var i = 0; i < salary.length; i++) {
     document.write(salary[i] + "<br>" );
}
</script>

输出如下：

Original array :
ABC, 24, 18000
EFG, 30, 30000
IJK, 28, 41000
EFG, 31, 28000

after adding "India" at the 4th array :
ABC, 24, 18000
EFG, 30, 30000
IJK, 28, 41000
EFG, 31, 28000, India

after adding "USA" and "Canada" at the 3rd array using "push()" method :
ABC, 24, 18000
EFG, 30, 30000
IJK, 28, 41000, USA, Canada
EFG, 31, 28000, India

范例5：

// Prints a simple multidimensional array in
// JavaScript where we add a new inner array 
<script>
var salary = [
    [ "ABC" , 24, 18000], [ "EFG" , 30, 30000], [ "IJK" , 28, 41000], [ "EFG" , 31, 28000], ]; 
  
// Prints first array
document.write( "Original array :<br>" );
  
for ( var i = 0; i < salary.length; i++) {
     document.write(salary[i] + "<br>" );
}
  
document.write( "<br>After adding a new inner array :<br>" );
  
// Pushing a new sub-array
salary.push([ "MNO" , 29, 33300]);
  
for ( var i = 0; i < salary.length; i++) {
     document.write(salary[i] + "<br>" );
}
</script>

输出如下：

Original array :
ABC, 24, 18000
EFG, 30, 30000
IJK, 28, 41000
EFG, 31, 28000

After adding a new inner array :
ABC, 24, 18000
EFG, 30, 30000
IJK, 28, 41000
EFG, 31, 28000
MNO, 29, 33300

范例6：

// Prints a simple multidimensional array in
// JavaScript where we remove a single element
//and a entire sub-array
<script>
var salary = [
    [ "ABC" , 24, 18000], [ "EFG" , 30, 30000], [ "IJK" , 28, 41000], [ "EFG" , 31, 28000], ]; 
  
// Prints first array
document.write( "Original array :<br>" );
  
for ( var i = 0; i < salary.length; i++) {
     document.write(salary[i] + "<br>" );
}
  
document.write( "<br>After removing last element " 
             + "of last inner array :<br>" );
  
// Removes the last element of 3rd sub-array
salary[3].pop();
  
for ( var i = 0; i < salary.length; i++) {
     document.write(salary[i] + "<br>" );
}
  
document.write( "<br>After removing last inner array :<br>" );
  
// Removes last sub-array
salary.pop();
  
for ( var i = 0; i < salary.length; i++) {
     document.write(salary[i] + "<br>" );
}
</script>

输出如下：

Original array :
ABC, 24, 18000
EFG, 30, 30000
IJK, 28, 41000
EFG, 31, 28000

After removing last element of last inner array :
ABC, 24, 18000
EFG, 30, 30000
IJK, 28, 41000
EFG, 31

After removing last inner array :
ABC, 24, 18000
EFG, 30, 30000
IJK, 28, 41000

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