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Remove elements from javascript array (opposite intersection)

Yesterday I resolved this question Remove elements from javascript array But I was wrong, my explanation and my example were about intersection of two arrays.
I wanted to ask how to remove elements in an array that do not exist in another array.
Example :

Array A=> [a, b, c, d]  
Array B=> [b, d, e]  
Array C= removeElementsNotIn(A, B);  
Array C (after function)-> [a,c]

Many thanks.

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3 answers


You can use .filter()

to selectively remove items that fail the test.

var c = a.filter(function(item) { 
    return b.indexOf(item) < 0; // Returns true for items not found in b.
});

In function:



function removeElementsNotIn(a, b) {
    return a.filter(function(item) { 
       return b.indexOf(item) < 0; // Returns true for items not found in b.
    });
}
var arrayC = removeElementsNotIn(arrayA, arrayB);

If you want to get really fancy (advanced only), you can create a function that returns a filter function, like this:

function notIn(array) {
    return function(item) {
        return array.indexOf(item) < 0;
    };
}
// notIn(arrayB) returns the filter function.
var c = arrayA.filter(notIn(arrayB));
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Thanks second Rihdo full code:

var a = [1,2,3,4,5];
var b = [4,5,6,7,8,9];

var new_array = a.filter(function(item) { 
  return b.indexOf(item) < 0; // Returns true for items not found in b.
});
alert(new_array);
// results: array[1,2,3]


Demo: https://jsfiddle.net/cmoa7Lw7/

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a1 = ['s1', 's2', 's3', 's4', 's5'];
a2 = ['s4', 's5', 's6'];
a3 = [];

function theFunction(ar1, ar2) {
  var ar3 = [];
  for (var i = 0; i < a1.length; i++) {
    if (ar2.indexOf(ar1[i]) != -1) {
      ar3.push(ar1[i]);
    }
  }
  return ar3;
}

a3 = theFunction(a1, a2);

document.getElementById('out').innerHTML = a3.toString();
      

        
        
        
      

    
<div id="out"></div>
Run codeHide result


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