Object Array Filtering On Multiple Properties With underscore.js

Question

Given the following array of objects:

var files = [{
    name: "test1",
    size: 123
}, {
    name: "test1",
    size: 456
}, {
    name: "test2",
    size: 789
}]

If I wanted a new array without the object with the name "test1" and the size 123 the following makes sense to me:

_.filter(files, function(_file) {
    return _file.name !== "test1" && _file.size !== 123;
});

However; this always removes both items with the name "test1". The following returns the desired results:

_.filter(files, function(_file) {
    return _file.name !== "test1" || _file.size !== 123;
});

How come?

thefourtheye · Accepted Answer · 2015-10-02 16:01:54Z

1

Your actual condition should have been

return !(_file.name === "test1" && _file.size === 123);

because you have to reject items only if both the properties match the specific values, not when any of the properties do not match the specific values.

In your code, for the second element, _file.name !== "test1" is actually false and the entire expression becomes false, so the second item is also skipped.

answered Oct 2, 2015 at 16:01

thefourtheye

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