Question

I have a two-dimensional array like this:

all = [
    [bla, bla, ID1, bla, bla],
    [bla, bla, ID2, bla, bla],
    [bla, bla, ID3, bla, bla],
    [bla, bla, ID4, bla, bla],
    [bla, bla, ID5, bla, bla],
    [bla, bla, ID6, bla, bla]
]

Next, I have a one-dimensional array like this:

selected = [ID1, ID2, ID6]

I need to remove all entries from my array all where the ID value does not match any ID in my array selected. From the example above I would then get a new array like this:

reduced = [
    [bla, bla, ID1, bla, bla],
    [bla, bla, ID2, bla, bla],
    [bla, bla, ID6, bla, bla]
]

How can I get an array like this?

Thanks for helping.

Answer 1

You can one line this using Array.prototype.filter

var reduced = all.filter(function (a) {return selected.indexOf(a[2]) !== -1;});

It simply means, if all[i][2] (the value from the ID col) is in the selected array, keep this entry. It builds a new Array so all and selected won’t be affected by this process.

It may be slightly faster to use a loop to do the same test, as it will mean less function overhead

var reduced = [], i = 0;
for (; i<all.length; ++i)
    if (selected.indexOf(all[i][2]) !== -1)
        reduced[reduced.length] = all[i];