I have an array here:

a = [1, 1, 2, 3, 4, 5, 5, 6, 7, 7]

and another,

b = [1, 2, 5]

I want to find all occurrences of each element of array b in a. i.e. I want a resultant array like this:

result = [1, 1, 2, 5, 5]

I was going through the Lodash docs to find any bination of methods which would give me the result, but haven't managed to do so. Does anyone know how I can get the result array? I prefer to use a very concise solution (i.e. without too many loops etc), and usually Lodash is best for that, but other solutions are also fine.

I have an array here:

a = [1, 1, 2, 3, 4, 5, 5, 6, 7, 7]

and another,

b = [1, 2, 5]

I want to find all occurrences of each element of array b in a. i.e. I want a resultant array like this:

result = [1, 1, 2, 5, 5]

I was going through the Lodash docs to find any bination of methods which would give me the result, but haven't managed to do so. Does anyone know how I can get the result array? I prefer to use a very concise solution (i.e. without too many loops etc), and usually Lodash is best for that, but other solutions are also fine.

• javascript
• arrays
• lodash

3 Answers 3

You'd just filter the first array based on the second array

var a = [1, 1, 2, 3, 4, 5, 5, 6, 7, 7];
var b = [1, 2, 5];

var result = a.filter( z => b.indexOf(z) !== -1 );

console.log(result);

You can use for..of loops to iterate b check if element of a is equal to current element in b

let a = [1, 1, 2, 3, 4, 5, 5, 6, 7, 7];

let b = [1, 2, 5];

let result = [];

for (let prop of b) {
  for (let el of a) {
    if (el === prop) result = [...result, el]
  }
}

console.log(result);

If you really wanted to use _, you could use 2 _.difference calls.

var a = [1, 1, 2, 3, 4, 5, 5, 6, 7, 7];
var b = [1, 2, 5];

var result = _.difference(a,_.difference(a,b));

console.log(result);

<script src="https://cdn.jsdelivr/lodash/4.16.4/lodash.min.js"></script>