How to check first element of an array 1 with all elements in array 2, then second element in array 2, repeat, using JS for loop? or a JS method?

Question

var array1 = ['1','2','3','4','5','6','7']

var array2 = ['43','24','35','42','55','63','1']

So, in the above code, we would check all elements in array1 against 43, then all elements in array 1 against 24 etc.

The output would remove any instances from array1 that match any instances in array 2 and add it to the end. So the output would be

array1 = ['2','3','4','5','6','7', '1']

The output would remove any instances from array1 that match any instances in array 2 and add it to the end. So the output would be var array1 = ['2','3','4','5','6','7', '1'] — Leafyshark, Dec 21 '17 at 10:18
@MagicJS, so you want the element that is on array2 to be added to the last? — Sunil Lama, Dec 21 '17 at 10:27
@Sunil Lama https://www.freecodecamp.org/challenges/pig-latin, I'm trying to remove the first cluster of consonants (if they are consonants, not vowels) and add them to the end of the array. — Leafyshark, Dec 21 '17 at 15:35

score 0 · Answer 1 · answered Dec 21 '17 at 10:22

0

u can do that with simple loop or u can use lodash library:)

_.difference([2, 1], [2, 3]);

// => [1]

answered Dec 21 '17 at 10:22

Vasyl Gutnyk

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score 0 · Answer 2 · answered Dec 21 '17 at 10:27

You can do this by using forEach on first array.

For example:

array1.forEach(elem1 => {
  var index = array2.indexOf(elem1);
  if (index != -1) {
    array2.splice(index, 1);
  } else {
    array2.push(elem1);
  }
});

In this example you iterate through array1 and search for position of each array1 element. If you find one, then it will be removed.

score 0 · Answer 3 · answered Dec 21 '17 at 10:36

You can use array#reduce to segregate values of array1 into unique array and repeating array and then array#concat both of them.

var array1 = ['1','2','3','4','5','6','7'],
    array2 = ['43','24','35','42','55','63','1'],
    set = new Set(array2);
    
var result = array1.reduce((r,v) => (set.has(v) ? r.repeating.push(v) : r.unique.push(v), r), {unique:[], repeating:[]});

var output = result.unique.concat(result.repeating);

console.log(output);

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You can also use array#includes to check for value in the other array.

var array1 = ['1','2','3','4','5','6','7'],
    array2 = ['43','24','35','42','55','63','1'];
    
var result = array1.reduce((r,v) => (array2.includes(v) ? r.repeating.push(v) : r.unique.push(v), r), {unique:[], repeating:[]});

var output = result.unique.concat(result.repeating);

console.log(output);

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How to check first element of an array 1 with all elements in array 2, then second element in array 2, repeat, using JS for loop? or a JS method?

3 Answers3