What is the best way to locate the position of an element within an Array with underscore.js?

Question

What is the best way to locate the position of an element within an Array with underscore.js?

I need assistance with finding the index of a specific value within an array using underscore.js.

Here is the scenario I am facing:

var array = [{'id': 1, 'name': 'xxx'},
             {'id': 2, 'name': 'yyy'},
             {'id': 3, 'name': 'zzz'}];

var searchValue = {'id': 1, 'name': 'xxx'};

I have attempted to use the following code:

var index = _.indexOf(array, function(data) { 
                alert(data.toSource()); //For testing purpose 
                return data === searchValue; 
            });

I also tried this alternative approach:

var index = _.indexOf(array, {id: searchValue.id});

Unfortunately, both methods return -1 which indicates that the function was not entered. As a result, the alert message did not appear.

I am seeking help in identifying what is incorrect with my code. Can anyone provide guidance?

javascript angularjs underscore.js javascript-framework

Answer 1

Answer №1

If you're looking for a library with handy functions that are missing in underscore, I highly recommend checking out lodash.

Here's an example of how you can use lodash:

var array = [{'id': 1, 'name': 'xxx'},
           {'id': 2, 'name': 'yyy'},
           {'id': 3, 'name': 'zzz'}];

var searchValue = {'id': 1, 'name': 'xxx'};


var index = _.findIndex(array, searchValue); 
console.log(index === 0); //-> true

http://lodash.com/docs#findIndex

If you're sticking with Underscore but want to access lodash's features, you can get lodash's underscore build from

ES2015

With ES2015 being widely used now (thanks to transpilers like Babel), you have the option to skip using lodash and underscore and utilize native methods instead:

var arr = [{ id: 1 }, { id: 2}];

arr.findIndex(i => i.id === 1); // 0

Answer 2

If you're looking for a library with handy functions that are missing in underscore, I highly recommend checking out lodash.

Here's an example of how you can use lodash:

var array = [{'id': 1, 'name': 'xxx'},
           {'id': 2, 'name': 'yyy'},
           {'id': 3, 'name': 'zzz'}];

var searchValue = {'id': 1, 'name': 'xxx'};


var index = _.findIndex(array, searchValue); 
console.log(index === 0); //-> true

http://lodash.com/docs#findIndex

If you're sticking with Underscore but want to access lodash's features, you can get lodash's underscore build from

ES2015

With ES2015 being widely used now (thanks to transpilers like Babel), you have the option to skip using lodash and underscore and utilize native methods instead:

var arr = [{ id: 1 }, { id: 2}];

arr.findIndex(i => i.id === 1); // 0

Answer 3

Answer №2

Here is an alternative solution:

let items = [{'id': 1, 'name': 'xxx'},
             {'id': 2, 'name': 'yyy'},
             {'id': 3, 'name': 'zzz'}];

let searchValue = {'id': 1, 'name': 'xxx'};
let index = -1;

_.each(items, function(item, idx) { 
   if (_.isEqual(item, searchValue)) {
      index = idx;
      return;
   }
});

console.log(index); //0

When comparing objects in your code snippet, data === searchValue compares the object references, which may not be what you intend. Using data == searchValue would compare string representations instead. To accurately compare objects, use _.isEqual.

Answer 4

Here is an alternative solution:

let items = [{'id': 1, 'name': 'xxx'},
             {'id': 2, 'name': 'yyy'},
             {'id': 3, 'name': 'zzz'}];

let searchValue = {'id': 1, 'name': 'xxx'};
let index = -1;

_.each(items, function(item, idx) { 
   if (_.isEqual(item, searchValue)) {
      index = idx;
      return;
   }
});

console.log(index); //0

When comparing objects in your code snippet, data === searchValue compares the object references, which may not be what you intend. Using data == searchValue would compare string representations instead. To accurately compare objects, use _.isEqual.

Answer 5

Answer №3

Perhaps my suggestion could offer some valuable insight.

Is there a specific reason you are using callback for the indexOf method? In underscore.js, the signature of indexOf is as follows:

_.indexOf(array, value, [isSorted])

Consider using find for this task instead:

_.find(array, function(item, index) {
  if (item.id === searchValue.id) {
    alert(index);
  }
});

Answer 6

Perhaps my suggestion could offer some valuable insight.

Is there a specific reason you are using callback for the indexOf method? In underscore.js, the signature of indexOf is as follows:

_.indexOf(array, value, [isSorted])

Consider using find for this task instead:

_.find(array, function(item, index) {
  if (item.id === searchValue.id) {
    alert(index);
  }
});

Answer 7

Answer №4

When it comes to objects, the comparison operators === and == are used to determine if two references point to the same object, not necessarily equivalent objects:

var a = {foo: "bar"};
var b = {foo: "bar"};
console.log(a === b); // false, `a` and `b` refer to different (but equivalent) objects
a = b = {something: "here"};
console.log(a === b); // true, `a` and `b` refer to the *same* object

To make a decision about object equality, you need to compare their properties. In this scenario, the id property seems like a good candidate for comparison. Alternatively, if you want to compare all properties, you could utilize Underscore's isEqual method.

Answer 8

When it comes to objects, the comparison operators === and == are used to determine if two references point to the same object, not necessarily equivalent objects:

var a = {foo: "bar"};
var b = {foo: "bar"};
console.log(a === b); // false, `a` and `b` refer to different (but equivalent) objects
a = b = {something: "here"};
console.log(a === b); // true, `a` and `b` refer to the *same* object

To make a decision about object equality, you need to compare their properties. In this scenario, the id property seems like a good candidate for comparison. Alternatively, if you want to compare all properties, you could utilize Underscore's isEqual method.

Answer 9

Answer №5

When utilizing Underscore, it prioritizes using the native indexOf method if accessible; otherwise, it resorts to a fallback option. Therefore, when dealing with a list of objects, an alternative implementation is necessary.

For instance, consider the following:

_.chain(array).pluck("key").indexOf("value").value();

or

_.map(array,function(e) { return e.key; }).indexOf(value);

Answer 10

When utilizing Underscore, it prioritizes using the native indexOf method if accessible; otherwise, it resorts to a fallback option. Therefore, when dealing with a list of objects, an alternative implementation is necessary.

For instance, consider the following:

_.chain(array).pluck("key").indexOf("value").value();

or

_.map(array,function(e) { return e.key; }).indexOf(value);

Answer 11

Answer №6

If you're dealing with intricate objects and need to search for a specific property within the collection, you can use this simple method:

 _.indexOf(arrayObj, _.findWhere(arrayObj, {key: "value"}));

In this code snippet, "arrayObj" represents the array containing the objects, "key" is the property you are searching for, and "value" is the desired value.

Answer 12

If you're dealing with intricate objects and need to search for a specific property within the collection, you can use this simple method:

 _.indexOf(arrayObj, _.findWhere(arrayObj, {key: "value"}));

In this code snippet, "arrayObj" represents the array containing the objects, "key" is the property you are searching for, and "value" is the desired value.

Answer 13

Answer №7

Currently implementing the findIndex method in my code.

 _.findIndex(myArray, valueToSearch);

Answer 14

Currently implementing the findIndex method in my code.

 _.findIndex(myArray, valueToSearch);

Answer 15

Answer №8

_.searchArray(array, function(element, position) {
  if (element.identifier == targetValue.identifier) {
    displayAlert(position);
  }
});

Answer 16

_.searchArray(array, function(element, position) {
  if (element.identifier == targetValue.identifier) {
    displayAlert(position);
  }
});

What is the best way to locate the position of an element within an Array with underscore.js?

Answer №1

ES2015

Answer №2

Answer №3

Answer №4

Answer №5

Answer №6

Answer №7

Answer №8

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