Predicate Sample

list.ts

type Predicate<T> = (item: T) => boolean;

function filter<T> (source : T[], callback : Predicate<T>) {
    const temp = [];
        
    for (let item of source) {

        if (callback(item)) {
            temp.push(item);
        }
    }

    return temp;
}

class List<T> extends Array<T>
{
    constructor(...items: T[])
    {
        super();
        for (let item of items){
            this.push(item);
        }
    }

    public where = (predicate: Predicate<T>): List<T> =>
    {
        const temp: List<T> = new List<T>();
        
        for (let item of this) {

            if (predicate(item)) {
                temp.push(item);
            }
        }

        return temp;
    }
}


// Usage

const workers = new List<number>(1, 2, 3, 4, 5, 6, 7, 8, 9, 0);

let items = filter(workers, x => x > 6); // 7, 8, 9
items = workers.where(x => x > 6); // 7, 8, 9