Question

67

rated 0 times [ 69] [ 2] / answers: 1 / hits: 87220 / 10 Years ago, tue, january 20, 2015, 12:00:00

I have this array:

var fruits = ['Apple', 'Banana', 'Orange', 'Celery'];

And I use Lodash's remove like so:

_.remove(fruits, function (fruit) {

  return fruit === 'Apple' || 'Banana' || 'Orange';

})

The result is ['Apple', 'Banana', 'Orange', 'Celery'], while I expected it to be ['Apple', 'Banana', 'Orange']. Why is this so?

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Location: Turkmenistan

Member since Sat, Apr 16, 2022

2 Years ago

answered 10 Years ago bryantc · Accepted Answer

Because when fruit is Celery, you are testing:

Celery === 'Apple' || 'Banana' || 'Orange'

which evaluates to

false || true || true

which is true.

You can't use that syntax. Either do it the long way around:

_.remove(fruits, function (fruit) {

  return fruit === 'Apple' || fruit === 'Banana' || fruit === 'Orange'

});

or test for array membership:

_.remove(fruits, function (fruit) {

  return _.indexOf(['Apple', 'Banana', 'Orange'], fruit) !== -1

});

This is not limited to JavaScript, and is in fact a common mistake (e.g. this question)