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.

Answer 1

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.