CODEWITHSUNDEEP
javascriptloopsfiltercallbackhigher-order-functions
Mateusz Osuch
Mateusz Osuch

Reputation: 357

How to return booleans joined with && inside callback function in filter method?

I am looking for an elegant way to generate booleans that will eventually be joined using && operator inside my callback function in filter method.

I tried to loop through the filter conditions but I cannot find a way to join each iteration result into the following format:

return Boolean && Boolean && Boolean && Boolean && Boolean

Becasue += && Boolean doesn't work.

Here is what I have and what is working:

//data I am filtering
this.preSearch = [
  ["The Lord of the Rings", "J. R. R. Tolkien", "English", "1955", "150 milionów"],
  ["Le Petit Prince (The Little Prince)", "Antoine de Saint-Exupéry", "French", "1943", "140 milionów"],
  ["Harry Potter and the Philosopher's Stone", "J. K. Rowling", "English",  "1997", "120 milionów"],
  ["The Hobbit", "J. R. R. Tolkien", "English", "1937", "100 milionów"],
  ["And Then There Were None", "Agatha Christie",   "English", "1939",  "100 milionów"],
  ["Dream of the Red Chamber",  "Cao Xueqin",   "Chinese", "1791", "100 milionów"]
]

//filters, that are set dynamically but let's pretend they are equal to
var filters = ["", "", "english", "19", "1"]

var searchdata = this.preSearch.filter(row => {
          return 
    row[0].toLowerCase().indexOf(filters[0].toLowerCase()) > -1 
    && row[1].toLowerCase().indexOf(filters[1].toLowerCase()) > -1 
    && row[2].toLowerCase().indexOf(filters[2].toLowerCase()) > -1 
    && row[3].toLowerCase().indexOf(filters[3].toLowerCase()) > -1 
    && row[4].toLowerCase().indexOf(filters[4].toLowerCase()) > -1
})

I need scalable and way more elegant solution so I will not have to add another line with && if I enhance my filtered array.

Upvotes: 1

Views: 97

Answers (2)

Nina Scholz
Nina Scholz

Reputation: 386746

You could use Array#every for the filters array.

For a faster check, you could convert the filter values to lowercase in advance.

var preSearch = [["The Lord of the Rings", "J. R. R. Tolkien", "English", "1955", "150 milionów"], ["Le Petit Prince (The Little Prince)", "Antoine de Saint-Exupéry", "French", "1943", "140 milionów"], ["Harry Potter and the Philosopher's Stone", "J. K. Rowling", "English", "1997", "120 milionów"], ["The Hobbit", "J. R. R. Tolkien", "English", "1937", "100 milionów"], ["And Then There Were None", "Agatha Christie", "English", "1939", "100 milionów"], ["Dream of the Red Chamber", "Cao Xueqin", "Chinese", "1791", "100 milionów"]],
    filters = ["", "", "english", "19", "1"].map(s => s.toLowerCase()),
    result = preSearch
        .filter(row => filters.every((v, i) => row[i].toLowerCase().includes(v)));

console.log(result);
.as-console-wrapper { max-height: 100% !important; top: 0; }

Upvotes: 3

Duncan Thacker
Duncan Thacker

Reputation: 5188

You can do this by applying Array.every() and String.includes() like this:

var searchdata = this.preSearch.filter(row => {

    // this only returns true if our condition works for
    // index = 0, 1, 2, 3, 4
    return [0, 1, 2, 3, 4].every(index => {
        const rowContent = row[index].toLowerCase();
        const filterContent = filters[index].toLowerCase();

        // String.includes() is nicer than String.indexOf() here because
        // you don't need the ugly -1
        return rowContent.includes(filterContent);
    });
});

Upvotes: 1

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