在Javascript中查找另一个数组中数组的每个元素的所有出现

Question

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 . ie I want a resultant array like this:

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

I was going through the Lodash docs to find any combination 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 (ie without too many loops etc), and usually Lodash is best for that, but other solutions are also fine.

Answer 1

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); 

Answer 2

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); 

Answer 3

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); 

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