CODEWITHSUNDEEP
javascriptarrays
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Reputation: 6868

Set value of property if value is in array

Below is my main array:

var myArray = [
    {field: 'Saab', flag: false}, 
    {field: 'cStatus', flag: false}, 
    {field: 'BMW', flag: false},
    {field: 'Mercedes', flag: false}
];

var cars1 = ["Saab", "Bmw"];

I am trying to set property flag to true of myArray objects, whose field property is included in the cars1 variable.

Expected output in myArray variable only:

myArray = [
    {field: 'Saab', flag: true}, 
    {field: 'Volvo', flag: false}, 
    {field: 'BMW', flag: true},
    {field: 'Mercedes', flag: false}
];

Can anybody please show me how to do this? I've tried the following:

var myArray = [
    {field: 'Saab', flag: false}, 
    {field: 'Volvo', flag: false}, 
    {field: 'BMW', flag: false},
    {field: 'Mercedes', flag: false}
];
var cars1 = ["Saab", "BMW"]; 

console.log(myArray.filter(x => cars1.indexOf(x.field) > -1));

Upvotes: 0

Views: 73

Answers (4)

Andrew Li
Andrew Li

Reputation: 57944

You can utilize Array.prototype.indexOf and Array.prototype.forEach to iterate over the array and check if cars1 contains field:

var myArray = [
    {field: 'Saab', flag: false}, 
    {field: 'Volvo', flag: false}, 
    {field: 'BMW', flag: false},
    {field: 'Mercedes', flag: false}
];
var cars1 = ["Saab", "BMW"]; 

myArray.forEach(car => car.flag = cars1.indexOf(car.field) > -1);
console.log(myArray);

The above iterates over the array and car represents the current object. Then we assign car.flag to the result of cars1.indexOf(car.field) > -1. The result will be true if cars1 contains the field, and false if it does not.

You can also use Array.prototype.includes to check if the array includes a certain value, though it's not supported on all browsers (most do). This will get rid of the indexOf check:

var myArray = [
    {field: 'Saab', flag: false}, 
    {field: 'Volvo', flag: false}, 
    {field: 'BMW', flag: false},
    {field: 'Mercedes', flag: false}
];
var cars1 = ["Saab", "BMW"]; 

myArray.forEach(car => car.flag = cars1.includes(car.field));
console.log(myArray);

Upvotes: 1

Nina Scholz
Nina Scholz

Reputation: 386560

You could use Set for the cars and iterate then only myArray.

The key part is a callback which uses a closure over a set with the content of cars1

myArray.forEach(
    (cars => o => cars.has(o.field) && (o.flag = true))(new Set(cars1))
);

which basically is in the first step

    (cars => o => cars.has(o.field) && (o.flag = true))(new Set(cars1))
    (cars =>                                          )(new Set(cars1))
//   ^^^^                                                               closure over
//                                                      ^^^^^^^^^^^^^^  set with car values

Inside of the returned function a check is made, if field is in the set and then the assignment of true to o.flag takes place.

             o => cars.has(o.field) && (o.flag = true)
//           ^                                          currentValue of array
//                ^^^^^^^^^^^^^^^^^                     check if field is in set
//                                  ^^                  if true
//                                     ^^^^^^^^^^^^^^^  evaluate expression
//                                                      assign true to o.flag 


var myArray = [{ field: 'Saab', flag: false }, { field: 'cStatus', flag: false }, { field: 'BMW', flag: false }, { field: 'Mercedes', flag: false }],
    cars1 = ["Saab", "Bmw"];

myArray.forEach((cars => o => cars.has(o.field) && (o.flag = true))(new Set(cars1)));

console.log(myArray);

Upvotes: 1

Matt Fernandez
Matt Fernandez

Reputation: 188

Hey Learning you can use the forEach method to loop through your 'myArray' and then use the .find method on cars1 for each iteration through your array. If cars1.find, finds a that equals the current cars field, then it will set that value.flag to true. If it does not, it will set it to false.

Here is a link to the .find() method https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/find

I hope this helps!

var myArray = [
  {field: 'Saab', flag: false}, 
  {field: 'Volvo', flag: false}, 
  {field: 'BMW', flag: false},
  {field: 'Mercedes', flag: false}
];

var cars1 = ["Saab", "BMW"]; 

myArray.forEach(value => {
  cars1.find((v) => v === value.field) ? value.flag = true : value.flag = false;
})

Upvotes: 1

kind user
kind user

Reputation: 41893

One of the ways how to solve it, is to use Array#some to check if specified element from the myArray exists in the cars1 array. If it does - set flag to true.

var myArray=[{field:"Saab",flag:false},{field:"cStatus",flag:false},{field:"BMW",flag:false},{field:"Mercedes",flag:false}],
    cars1 = ["Saab", "BMW"]; 

    myArray.forEach(v => cars1.some(c => c == v.field ? v.flag = true : null));
    console.log(myArray);

Upvotes: 1

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