CODEWITHSUNDEEP
javascriptarrays
icicleking
icicleking

Reputation: 1077

Slice Up array according to content

I have a somewhat complicated task of slicing and dicing an array of data into a sensible JSON Object. The first step is to slice the array into smaller arrays based on the content of the elements.

In this simplified version I want to break one big array into a series of smaller arrays defined by the word "that."

Given this array: 

that, thing, thing, that, thing, that, thing, thing, thing

I want to return:

[that, thing, thing],
[that, thing],
[that, thing, thing, thing],

Upvotes: 2

Views: 112

Answers (5)

Stephen James
Stephen James

Reputation: 86

You can use lastIndexOf, slice and unshift.

function test (a, b, item) {
  var i = a.lastIndexOf(item);
  while (i != -1) {
    b.unshift(a.slice(i));
    a = a.slice(0, i);
    i = a.lastIndexOf(item);
  }
  return b;
}

var arr1 = [1, 2, 3, 1, 2, 1, 2, 3, 4];
var arr2 = [];

test(arr1, arr2, 1);
console.log(arr2);

Using nodejs to run the result is:

[ [ 1, 2, 3 ], [ 1, 2 ], [ 1, 2, 3, 4 ] ]

Upvotes: 0

Matt Burland
Matt Burland

Reputation: 45135

A quick reduce should fix it:

var src = ["that", "thing", "thing", "that", "thing", "that", "thing", "thing", "thing"]

var dest = src.reduce(function(p,d) {
    if (d === "that") {
        p.push([d]);
    } else {
        p[p.length-1].push(d);
    }
    return p;
},[]);

$("#json").text(JSON.stringify(dest));
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div id="json"></div>

Upvotes: 0

Dan O
Dan O

Reputation: 6090

this is easy to do with Array.reduce():

var array = ["that", "thing", "thing", "that", "thing", "that", "thing", "thing", "thing"];

console.log(array.reduce(function(prev, cur, idx, arr) {
    if (cur === "that") {
      // start a new sub-array
      prev.push(["that"]);
    }
    else {
      // append this token onto the current sub-array
      prev[prev.length - 1].push(cur);
    }

  return (prev);
}, []));

JSFiddle

Upvotes: 1

chowey
chowey

Reputation: 9836

This is going to be manual work. I recommend a combination of indexOf (to find the "that") and splice (to remove the relevant sub-array).

var input = ["that", "thing", "thing", "that", "thing", "that", "thing", "thing", "thing"];
var output = [];
for (var idx = input.indexOf("that", 1); idx !== -1; idx = input.indexOf("that", 1)) {
    output.push(input.splice(0, idx));
}
output.push(input);

Upvotes: 0

Brant
Brant

Reputation: 1788

var arr = ['that', 'thing', 'thing', 'that', 'thing', 'that', 'thing', 'thing', 'thing'];
var subArrays = [];

var subArrayItem = [];
arr.forEach(function(arrItem) {
    if(arrItem == 'that') {
        if(subArrayItem.length) // avoid pushing empty arrays
            subArrays.push(subArrayItem)
        subArrayItem = []
    }
    subArrayItem.push(arrItem)
})

if(subArrayItem.length) // dont forget the last array
    subArrays.push(subArrayItem)

Upvotes: 1

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