How to separate an array based on another array

Question

So I have two array like this.

var array1 = ["str1", "str2", "str3", "str4", "str5", "str6"];

How can i split the array1 based on elements in array2 so that the result become like this and store in 3 array(not always 3,depends on array2's items)?

var array2 = ["str2","str5"];
// Case1 result 
// newArr1=["str1"]
// newArr2=["str2","str3","str4"]
// newArr3=["str5","str6"]

var array2 = ["str2","str3"];
//Case2 result
// newArr1=["str1"]
// newArr2=["str2"]
// newArr3=["str3","str4""str5","str6"]

I tried this and i have no idea how to achieve result like above.

for (i = 0; i < array2.length; i++) {
   newArr = array1.splice(0, array1.indexOf(array2[i]));
}

array2 acts as a breaking point. So if array2 contain all elements of array1. It should generate 6 new array with only one item in each.

Please help me in understanding the logic that will decide how many elements will go in each array — brk
– brk, Commented Dec 23, 2017 at 7:52
Is it acceptable to have the arrays back as arrays of arrays [["str1"],["str2","str3","str4"],["str5","str6"]]? — Kent Shikama
– Kent Shikama, Commented Dec 23, 2017 at 7:53
here ["str2","str5"] str2 and str5 are the breaking points in array1 — freelancer
– freelancer, Commented Dec 23, 2017 at 7:53
It's a good idea making your desired outcome perfectly clear. Otherwise, people will have to spend a lot of energy just to understand what you want (if they can), and most answerers (like me) will just move to the next question... on top of that, desired outcomes that are not exactly clear will generate a lot of wrong answers and downvotes, wasting everyone's time. — Gerardo Furtado
– Gerardo Furtado, Commented Dec 23, 2017 at 7:53
@GerardoFurtado +1, Like me, I am still trying to understand what really he/she want — Aria
– Aria, Commented Dec 23, 2017 at 7:55

freelancer · Accepted Answer · 2017-12-23 10:42:17Z

Here is the way to start and achieve as you want

var array1 = ["str1", "str2", "str3", "str4", "str5", "str6"];
var newArray = [];
var array2 = ["str1", "str2", "str3", "str4", "str5", "str6"];
var prev = 0;
for(let i in array2){
  var index = array1.indexOf(array2[i]);
  if(index != prev){
    newArray.push(array1.slice(prev,index));
    prev = index;
  }
}
newArray.push(array1.slice(prev));
console.log(newArray);

var array1 = ["str1", "str2", "str3", "str4", "str5", "str6"];
var newArray = [];
var array2 = ["str2", "str5"];
var prev = 0;
for(let i in array2){
  var index = array1.indexOf(array2[i]);
  if(index != prev){
    newArray.push(array1.slice(prev,index));
    prev = index;
  }
}
newArray.push(array1.slice(prev));
console.log(newArray);

Also with dynamic variable

var array1 = ["str1", "str2", "str3", "str4", "str5", "str6"];
var count = 1;
var array2 = ["str2", "str5"];
var prev = 0;
for(let i in array2){
  var index = array1.indexOf(array2[i]);
  if(index != prev){
    window['newArray'+ count++] = array1.slice(prev,index);
    prev = index;
  }
}
window['newArray'+ count++] = array1.slice(prev);
console.log('newArray1 : ',newArray1);
console.log('newArray2 : ',newArray2);
console.log('newArray3 : ',newArray3);

Nina Scholz · Accepted Answer · 2017-12-23 08:48:52Z

0

You could take a single loop and look for the separation element and build a new array with the chunks. Later add the rest to the result.

This version works for recurring items in the array for splitting.

function group(array, starts) {
    var index = 0,
        result = [];

    starts.forEach(function (v) {
        result.push(array.slice(index, index = array.indexOf(v, index)));
    });
    result.push(array.slice(index));
    return result;
}

console.log(group(["str1", "str2", "str3", "str4", "str5", "str6"], ["str2", "str5"]));
console.log(group(["str1", "str2", "str3", "str4", "str5", "str6"], ["str2", "str3"]));
console.log(group(["str1", "str2", "str3", "str4", "str5", "str6"], []));

.as-console-wrapper { max-height: 100% !important; top: 0; }

edited Dec 23, 2017 at 8:48

answered Dec 23, 2017 at 8:40

Nina Scholz

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Comments

Ori Drori · Accepted Answer · 2017-12-23 18:27:18Z

0

Using ES6 - Create a Set from the items of array2. Iterate array1 using Array#reduce. If there is no sub array, or the current string is found in array2 Set (using Set#has), add a new sub array. Always push the current string to the last sub array.

const groupByArray = (array1, array2) => {
  const array2Set = new Set(array2);
  
  return array1.reduce((r, s) => {
    if(!r[r.length - 1] || array2Set.has(s)) {
      r.push([]);
    }

    r[r.length - 1].push(s);

    return r;
  }, [])
};

const array1 = ["str1", "str2", "str3", "str4", "str5", "str6"];
console.log(groupByArray(array1, ["str2","str5"]));
console.log(groupByArray(array1, ["str2","str3"]));

edited Dec 23, 2017 at 18:27

answered Dec 23, 2017 at 8:41

Ori Drori

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