Get column from a two dimensional array

Question

How can I retrieve a column from a 2-dimensional array and not a single entry  I m doing this because I want to search for a string in one of the columns only so if there is another way to accomplish this please tell me     I m using the array defined this way   var array       At the end the size of this array is 20 col x3 rows  and I need to read the first row and check the existence of some phrase in it

User · Answer

x000D   x000D  function arrayColumn arr  n    x000D    return arr map x  gt  x n    x000D    x000D   x000D  var twoDimensionalArray     x000D     1  2  3   x000D     4  5  6   x000D     7  8  9  x000D     x000D   x000D  console log arrayColumn twoDimensionalArray  1    x000D   x000D   x000D

User · Answer

I have created a library matrix-slicer to manipulate with matrix items  So your problem could be solved like this   var m   new Matrix        1  2        3  4        m getColumn 1        gt   2  4    Possible it will be useful for somebody   -

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You have to loop through each element in the 2d-array  and get the nth column       function getCol matrix  col          var column              for var i 0  i lt matrix length  i               column push matrix i  col                    return column             var array    new Array 20   new Array 20   new Array 20        your 3x20 array     getCol array  0     Get first column

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var data           quot a1 quot    quot a2 quot    quot a3 quot          quot b1 quot    quot b2 quot    quot b3 quot          quot c1 quot    quot c2 quot    quot c3 quot       var col0   data map d   gt  d 0          a1    b1    c1     var col1   data map d   gt  d 1          a2    b2    c2

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Use Array prototype map   with an arrow function    x000D   x000D  const arrayColumn    arr  n    gt  arr map x   gt  x n    x000D   x000D  const twoDimensionalArray     x000D     1  2  3   x000D     4  5  6   x000D     7  8  9   x000D     x000D   x000D  console log arrayColumn twoDimensionalArray  0    x000D   x000D   x000D    Note  Array prototype map   and arrow functions are part of ECMAScript 6  and not supported everywhere  see ECMAScript 6 compatibility table

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Taking a column is easy with the map function      a two-dimensional array var two d     1 2 3   4 5 6   7 8 9        take the third column var col3   two d map function value index    return value 2         Why bother with the slice at all  Just filter the matrix to find the rows of interest   var interesting   two d filter function value index   return value 1   5        interesting is now   4 5 6     Sadly  filter and map are not natively available on IE9 and lower   The MDN documentation provides implementations for browsers without native support

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This function works to arrays and objects  obs  it works like array column php function  It means that an optional third parameter can be passed to define what column will correspond to the indices of return   function array column list  column  indice       var result       if typeof indice     undefined            result                for key in list              result list key  indice     list key  column        else          result                for key in list              result push  list key  column                return result      This is a conditional version   function array column conditional list  column  indice       var result       if typeof indice     undefined            result                for key in list              if typeof list key  column       undefined   amp  amp  typeof list key  indice       undefined                   result list key  indice     list key  column        else          result                for key in list              if typeof list key  column       undefined                   result push  list key  column                return result      usability   var lista        1  2  3      4  5  6      7  8  9      var obj list        a  1  b  2  c  3      a  4  b  5  c  6      a  8  c  9      var objeto       d   a  1  b  3     e   a  4  b  5  c  6     f   a  7  b  8  c  9      var list obj       d   1  2  3     e   4  5     f   7  8  9      console log   column list     array column lista  1     console log   column obj list     array column obj list   b    c      console log   column objeto     array column objeto   c      console log   column list obj     array column list obj  0  0      console log   column list conditional     array column conditional lista  1     console log   column obj list conditional     array column conditional obj list   b    c      console log   column objeto conditional     array column conditional objeto   c      console log   column list obj conditional     array column conditional list obj  0  0       Output      column list   Array   2  5  8   column obj list   Object   3  2  6  5  9  undefined   column objeto   Array   undefined  6  9   column list obj   Object   1  1  4  4  7  7    column list conditional   Array   2  5  8   column obj list conditional   Object   3  2  6  5   column objeto conditional   Array   6  9   column list obj conditional   Object   1  1  4  4  7  7

User · Answer

You can use the following array methods to obtain a column from a 2D array   Array prototype map    const array column    array  column    gt  array map e   gt  e column      Array prototype reduce    const array column    array  column    gt  array reduce  a  c    gt      a push c column      return a            Array prototype forEach    const array column    array  column    gt      const result          array forEach e   gt        result push e column             return result         If your 2D array is a square  the same number of columns for each row   you can use the following method   Array prototype flat      filter    const array column    array  column    gt  array flat   filter  e  i    gt  i   array length     column

[javascript] Get column from a two dimensional array

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