javascript slicing an array on content

Question

Is there a way to slice with javascript an array but not according to the index of the dimension but according to the content of its' j-th element (supposedly uniqueness of values)?

Example:

myArray = [["a", "b", "c"], ["car", "hat", "plate"], ["red", "green", "black"]]

Slicing myArray on 0,1 will give

[["c"],["plate"],["black"]]

and slicing on "black" should give the same result.

What is the use of my question? Say for example that my array comes from parsing the rows of a file and I want to slice upon the headers (first row), but the headers of the -to be parsed- files (although same) come in random orders.

Thanks

What are the meaning of the parameters 0, 1? And why do these parameters produce the same value as calling with 'black' as a parameter? — Noah Freitas
– Noah Freitas, Commented Aug 14, 2015 at 2:18
Also, don't redefine Array; it's a constructor for arrays and redefining it will break a lot of things — MayThrow
– MayThrow, Commented Aug 14, 2015 at 2:22

Spencer Wieczorek · Accepted Answer · 2015-08-14 02:36:45Z

2

You can simply loop through the 2D array and call slice(j) on each array:

for(item in myArray)
    Array[item] = myArray[item].slice(2);

Here is an example snippet:

var myArray = [["a", "b", "c"], ["car", "hat", "plate"], ["red", "green", "black"]];

for(item in myArray)
    myArray[item] = myArray[item].slice(2);

console.log(myArray);

Using "black" as a paramter involes going through each array and finding such an element. When you find a match simply call indexOf() to get the proper index and use that, which will be 2:

var index = "black";

for(item in myArray)
    if(myArray[item].indexOf(index) != -1)
        index = myArray[item].indexOf(index);

// index = 2

Note: There will be problems when there is more than a single "black", in this case index will be the last "black" found in myArray.

edited Aug 14, 2015 at 2:36

answered Aug 14, 2015 at 2:14

Spencer Wieczorek

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8 Comments

Noah Freitas Over a year ago

This code happens to produce the right answer for the example, but it doesn't really make sense with some of the details of the question: namely, the parameters to the slice function (0, 1 and 'black').

Spencer Wieczorek Over a year ago

@NoahFreitas I think the OP means by 0,1 as to remove items in the 0,1 index and keep the ones at 2. and 'black' simply being the 2nd element of one of the arrays.

pebox11 Over a year ago

@NoahFreitas : You are correct Noah, I want to use "black" as a parameter and through time it may be on different indexes which I do not know.

Noah Freitas Over a year ago

@pebox11, and you want all the other arrays filtered down to only the value at the same index as 'black'?

Noah Freitas Over a year ago

@pebox11, this code does not currently do that, since it has the index (2) hard-coded. @codeSun's answer does suggest how to do this.

|

score 1 · Accepted Answer · 2015-08-15 04:16:47Z

1

If you want to use value of array element for search, use indexOf().

 myArray = [["a", "b", "c"], ["car", "hat", "plate"], ["red", "green", "black"]];

    var index = myArray.indexOf("black");

    for(value in myArray)
        myArray[value] = myArray[value].slice(index);

edited Aug 15, 2015 at 4:16

answered Aug 14, 2015 at 2:21

user5139444

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