如何使用UnderscoreJS进行条件过滤

Question

I just want to pull out an array element based on a condition.

I tried Underscore.js methods like _.filter and _.where methods, but I cannot get the desired output.

For more clarity, I don't want a car object where the price is > 80.

I tried with the code below and got an empty array back:

var carsArray = [{
    "name": "Record1",
    "bookings": [{
        "price": 50,
        "actualPrice": 70,
    }]
}, {
    "name": "Record2",
    "bookings": [{
        "price": 60,
        "actualPrice": 100,
    }]
}, {
    "name": "Record3",
    "bookings": [{
        "price": 100,
        "actualPrice": 110,
    }]
}];

var availableCars = _.filter(carsArray, function (items) {
    return _.filter(items, function (cars) {
        return(cars.price <= 80);
    });
});

Answer 1

For multiple elements in the bookings array

If there are multiple elements in the bookings array and to check if any of the element satisfies the condition Array#some can be used.

carsArray.filter(car => car.bookings.some(booking => booking.price <= 80));

To check if all the car booking prices are below 80 Array#every can be used.

carsArray.filter(car => car.bookings.every(booking => booking.price <= 80));

Live Demo:

 var carsArray = [{ "name": "Record1", "bookings": [{ "price": 50, "actualPrice": 70, }, { "price": 40, "actualPrice": 70 }] }, { "name": "Record2", "bookings": [{ "price": 60, "actualPrice": 100, }, { "price": 90, "actualPrice": 160 }] }, { "name": "Record3", "bookings": [{ "price": 100, "actualPrice": 110, }, { "price": 120, "actualPrice": 200 }] }]; var atLeastOne = carsArray.filter(car => car.bookings.some(booking => booking.price <= 80)); var allCars = carsArray.filter(car => car.bookings.every(booking => booking.price <= 80)); document.getElementById('some').innerHTML = JSON.stringify(atLeastOne, 0, 4); document.getElementById('every').innerHTML = JSON.stringify(allCars, 0, 4); 

 <strong>For any of the car bookings less than or equal to 80</strong> <pre id="some"></pre> <hr /> <strong>For all of the car bookings less than or equal to 80</strong> <pre id="every"></pre> 

---

For single element in bookings array

You can use JavaScript Array#filter with Arrow function as follow.

carsArray.filter(car => car.bookings[0].price <= 80);

 var carsArray = [{ "name": "Record1", "bookings": [{ "price": 50, "actualPrice": 70, }] }, { "name": "Record2", "bookings": [{ "price": 60, "actualPrice": 100, }] }, { "name": "Record3", "bookings": [{ "price": 100, "actualPrice": 110, }] }]; var filteredArr = carsArray.filter(car => car.bookings[0].price <= 80); console.log(filteredArr); document.getElementById('result').innerHTML = JSON.stringify(filteredArr, 0, 4); 

 <pre id="result"></pre> 

---

If there is only a single element in the bookings array, the format of the data can be changed as

var carsArray = [{
    "name": "Record1",
    "bookings": {
        "price": 50,
        "actualPrice": 70,
    }
}, {
    "name": "Record2",
    "bookings": {
        "price": 60,
        "actualPrice": 100,
    }
}, {
    "name": "Record3",
    "bookings": {
        "price": 100,
        "actualPrice": 110,
    }
}];

var filteredArr = carsArray.filter(car => car.bookings.price <= 80);

Answer 2

here's how to do it with underscorejs

var availableCars = _.filter(carsArray, function(car) {
    return _.any(car.bookings, function(booking) {
        return booking.price <= 80; 
    });
});

and here's how to do it in es6

var availableCars = carsArray.filter(car => car.bookings.some(booking => booking.price <= 80));

this ofcourse is if there are multiple bookings possible in a car and at least 1 booking is <= 80 buckeronies

Answer 3

I think what you want is this:

var availableCars = _.filter(carsArray, function(car){
  return _.every(car.bookings, function(booking) {
    return booking.price <= 80;
  });
});

I'm assuming each car can have more than one booking and that you want a car only if none of its booking was more than 80.

Answer 4

Thought I'd chip in with something that is closer to the requirement

I don't want a car object where the price is > 80

function expensiveBooking(booking){
    return booking.price > 80;
}

function carHasExpensiveBooking(car){
    return _.some(car.bookings, expensiveBooking);
}

var result = _.reject(carsArray, carHasExpensiveBooking);

Answer 5

Try this:

var availableCars = _.filter(carsArray, function(item){
    return (item.bookings.price <= 80);
    });
});