Angular 4 data filter with multiple condition

Question

I want to filter the data depending on multiple dropdowns(4 drop downs) selection.

I may choose any single dropdown or 2 dropdowns or multiple dropdowns. How can I add condition depending selection

this.gridData = this.dataProvider.filter(data => {
    return data.column1 == this.selectedFitler1
        && data.column2== this.selectedFitler2
        && data.column3 == this.selectedFitler3
        && data.column4 == this.selectedFitler4 })

Answer 1

let selectedFilter1 = ['val1a', 'val1b', 'va1e'];
...
let selectedFilter4 = ['val4a', 'val4c'];

this.gridData = this.dataProvider.filter(data => {
        return (selectedFilter1.findIndex(filterVal => filterVal === data.column1) !== -1 || selectedFilter1.length === 0)
            && selectedFilter2.findIndex(filterVal => filterVal === data.column2) !== -1 || selectedFilter2.length === 0)
            && selectedFilter3.findIndex(filterVal => filterVal === data.column3) !== -1 || selectedFilter3.length === 0)
            && selectedFilter4.findIndex(filterVal => filterVal === data.column4) !== -1 || selectedFilter4.length === 0)
    });

or if you know the types of the columns and do not want to repeat yourself:

isInSelected<T>(columnVal: T, filter: T[]): boolean {
    return filter.length === 0
        || filter.findIndex(filterVal => filterVal === columnVal) !== -1
}

and use it like this:

this.gridData = this.dataProvider.filter(data => {
        return this.isInSelected<string>(data.column1, this.selectedFilter1)
            && this.isInSelected<number>(data.column2, this.selectedFilter2)
            && this.isInSelected<number>(data.column3, this.selectedFilter3)
            && this.isInSelected<string>(data.column4, this.selectedFilter4);
    });