Javascript：如何创建多维数组？

Question

var mahasiswa = new Array();

mahasiswa[0] = new Array("100000001", "Alda",  "man",   "1 Mei 1994", "DKV");
mahasiswa[1] = new Array("100000002", "Aldi",  "woman", "2 Mei 1994", "Seni");
mahasiswa[2] = new Array("100000003", "Aldo",  "man",   "3 Mei 1994", "Seni");
mahasiswa[3] = new Array("100000004", "Alfi",  "man",   "4 Mei 1994", "Akutansi");
mahasiswa[4] = new Array("100000005", "Andi",  "man",   "5 Mei 1994", "Seni");
mahasiswa[5] = new Array("10000006" , "Bandri","woman", "6 Mei 1994", "DKV");

how I can print name of woman only? The name is at inex 1 (Alda/Aldi etc).

Answer 1

If you don't really need an array, it would be much easier to use an object.

Think of an object as a map with key value.

var mahasiswa = [];
 mahasiswa.push({
  id: "100000001",
  name:"Alda",
  gener: "man",
  someDate: "1 Mei 1994
 }); 
 mahasiswa.push({
  id: "100000001",
  name:"Alda",
  gender: "woman",
  someDate: "1 Mei 1994
 }); 

Then you could use something like this:

for(var i=0;i<mahasiswa.length;i++){
  var person = mahasiswa[i];

  if(person.gender === "woman"){ 
    console.log(mahasiswa[i].name)
 }
}

If you really need an Array, then do something like this:

for(i=0; i< mahasiswa.length; i++){
   var person = mahasiswa[i]; 
   if(person [2]=='woman'){
      console.log(person)
   }
}

Some background infos here: 1) If you initialize an array in Javascript, better use this the [] instead of new Array(). It's much faster (See this: http://jsperf.com/literal-vs-new-23 )

2) If possible, use an object over an array. it's much more flexible

3) Remember, objects are unsorted where arrays are sorted

Answer 2

I think the only way is to go through the whole array.

for(i=0;i<= mahasiswa.length;i++){
   if(mahasiswa[i][2]=='woman'){
      //...
   }
}

otherwise you should rearrange your array and sort it for gender in first dimension.

Answer 3

You can check if the entry is a woman by using this:

mahasiswa[n][2] == "woman"

So, using a for loop, you can print out the names of women only:

for (var i = 0, len = mahasiswa.length; i < len; i++){
  if (mahasiswa[i][2] == "woman"){
    console.log(mahasiswa[i][1]);
  }
}

But normally, in javascript, you wouldn't define an array like this as an array of arrays, but of objects.

Answer 4

Using this structure you can filter and map the array:

mahasiswa.filter( function( item ){ 
   return item[2] == "woman"; 
}).map( function( item ){ 
   return item[1] 
});  // ["Aldi", "Bandri" ]

http://jsfiddle.net/3vwo00ee/

Answer 5

You could use filter to get the 'woman' elements, and then just print the name(s) of each of them:

mahasiswa.filter(function (el) {
  return el[2] === 'woman';
}).forEach(function (el) {
  console.log(el[1])  
});