Sometimes, we want to filter a JavaScript array from all elements of another JavaScript array.
In this article, we’ll look at how to filter a JavaScript array from all elements of another array.
Using the Array.prototype.filter Method
We can use the JavaScript array filter method to filter out the array entries that are entries of another array.
For instance, we can write:
const filtered = [1, 2, 3, 4].filter(
function(e) {
return this.indexOf(e) < 0;
},
[2, 4]
);
console.log(filtered);
to do so.
We call filter on [1, 2, 3, 4] with a callback that calls this.indexOf(e) < 0 and return the result.
We set the value of this in the callback with the 2nd argument of filter .
Therefore, this is [2, 4] .
And so filtered is [1, 3] .
We cam also use the includes method to filter out the items that are in the other array.
For instance, we can write:
const filtered = [1, 2, 3, 4].filter(
function(e) {
return !this.includes(e);
},
[2, 4]
);
console.log(filtered);
And we get the same result for filter .
We can replace the callback with an array function if we don’t use this inside the callback.
To do this, we can write:
const filtered = [1, 2, 3, 4].filter(
(e) => {
return [2, 4].indexOf(e) < 0;
}
);
console.log(filtered);
or:
const filtered = [1, 2, 3, 4].filter(
(e) => {
return ![2, 4].includes(e);
}
);
console.log(filtered);
We replace this with the array itself.
And we get the same result.
Conclusion
We can use the JavaScript array filter instance method to return an array that has the items that are included in another array filtered out.
