Get and delete data from array in array

Question

I ran into a little bit of a problem with manipulation of data, since I don't know JavaScript too well. I have the following array:

var Dict = [["x", "y", "z"], ["x", "w", "m"], ["u", "t", "d", "L"]];

What I need is to select all first elements, then all the second elements etc. I've tried

for(var m in Dict) {
    First.push(m[0]);
    Second.push(m[1]);
    Third.push(m[2]);
}

But that doesn't seem to work. Then I also need to delete for example all "x" from the top array, which I haven't even attempted yet, because of the first problem.

It is an array. Use for (var i=0;i<dict.length;i++) or dict.forEach or a map — mplungjan
– mplungjan, Commented Feb 19, 2016 at 19:15

Billy Moon · Accepted Answer · 2016-02-19 19:25:17Z

1

var item, First=[], Second=[], Third=[], Dict = [["x", "y", "z"],["x", "w", "m"], ["u", "t", "d", "L"]];
for(var m in Dict) {
    // m does not refer to item in Dict, but index of item in Dict
    First.push(Dict[m][0]);
    Second.push(Dict[m][1]);
    Third.push(Dict[m][2]);
}
console.log(First, Second, Third);
// ["x", "x", "u"] ["y", "w", "t"] ["z", "m", "d"]

answered Feb 19, 2016 at 19:25

Billy Moon

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1 Comment

Ladislav Louka Over a year ago

Thanks, I wasnt sure in the indexes, and couldnt find a guide for arrays in arrays. Works like a charm

Rob M. · Accepted Answer · 2016-02-19 19:28:27Z

1

If you have access to es6, you can do this:

const Dict = [["x", "y", "z"],["x", "w", "m"], ["u", "t", "d", "L"]];
const [First, Second, Third] = Dict.map((_, i) => Dict.map(entry => return entry[i]));

The es5 version would be:

var Dict = [["x", "y", "z"],["x", "w", "m"], ["u", "t", "d", "L"]];
var Items = Dict.map(function(_, i) {
  return Dict.map(function(entry) {
    return entry[i];
  });
});

var First  = Items.shift(), 
    Second = Items.shift(), 
    Third  = Items.shift();

answered Feb 19, 2016 at 19:28

Rob M.

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Comments

stark · Accepted Answer · 2016-02-19 19:18:19Z

0

Try the following javascript, this should work :

var Dict = [
  ["x", "y", "z"],
  ["x", "w", "m"],
  ["u", "t", "d", "L"]
];
First = [];
Second = [];
Third = [];

for (m=0;m<Dict.length;m++) {
  First.push(Dict[m][0]);
  Second.push(Dict[m][1]);
  Third.push(Dict[m][2]);
}
console.log(First);
console.log(Second);
console.log(Third);

Gives the following three arrays :

["x", "x", "u"]
["y", "w", "t"]
["z", "m", "d"]

answered Feb 19, 2016 at 19:18

stark

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Comments

Đinh Carabus · Accepted Answer · 2016-02-19 19:24:39Z

0

Do not use for-in with arrays. To get all first elements:

ES5

var firstElements = Dict.map(function(el) { return el[0]; });

ES6

var firstElements = Dict.map(el => el[0]);

(yields ["x", "x", "u"])

edited Feb 19, 2016 at 19:24

answered Feb 19, 2016 at 19:14

Đinh Carabus

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Comments

A.Sharma · Accepted Answer · 2016-02-19 19:36:36Z

0

Try this:

var Dict = [["x", "y", "z"],["x", "w", "m"], ["u", "t", "d", "L"]];
var first = Dict.slice(0,1);
var second = Dict.slice(1,2);
var third = Dict.slice(-1);

To see what that produces go here:

JSFiddle

A Better Alternative

If you want to do it with a variable set of indices you can use splice instead of slice:

var Dict = [["x", "y", "z"],["x", "w", "m"], ["u", "t", "d", "L"]];
var result = [];
for(var i = 0; i < Dict.length; i++){
   result.push(Dict.splice(i));
}

You can see this here:

JSFiddle Splice

edited Feb 19, 2016 at 19:36

answered Feb 19, 2016 at 19:29

A.Sharma

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Comments

Godfrey Fernandes · Accepted Answer · 2016-02-19 21:42:53Z

0

Check this piece of code

var Dict = [["x", "y", "z"],["x", "w", "m"], ["u", "t", "d", "L"]];
for(var i=0; i < Dict.length;i++){
  allArr[i] = Dict.map(function(subArr){
    return subArr[i]
  });
  
  //To Remove all the "x" from the array
  if(i == 0){
    allArr[i] = allArr[i].filter(val => val != "x")
  }
}

answered Feb 19, 2016 at 21:42

Godfrey Fernandes

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