How to return not all of the properties of an object from arrays with an array method?

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I want to use an array method with arrow function. For an example:

const inventory = [
    {name: 'apples', quantity: 2, type: 'a'},
    {name: 'bananas', quantity: 0, type: 'a'},
    {name: 'cherries', quantity: 5, type: 'a'}
    {name: 'mangos', quantity: 5, type: 'a'}
];

const result = inventory.filter( fruit => fruit.quantity === 5 );

You'd create a new object. It looks like you want to do two things, though: Filter to only items with quantity of 5, and return objects without the quantity field. Unelss you have hundreds of thousands of these¹, you'd do that by using filter then map. Here's an example with destructuring:

const inventory = [
    {name: 'apples', quantity: 2, type: 'a'},
    {name: 'bananas', quantity: 0, type: 'a'},
    {name: 'cherries', quantity: 5, type: 'a'},
    {name: 'mangos', quantity: 5, type: 'a'}
];

const result = inventory
  .filter(fruit => fruit.quantity === 5)
  .map(({name, type}) => ({name, type}));

console.log(result);

Array methods, Here we can see that splice returns the array of removed elements: It returns a new array copying to it all items from index start to end (not including end ). Other objects, even if they look like arrays, are added as a whole: isConcatSpreadable property, then it's treated as an array by concat : its  Returning an object array has been explained above, but in most cases you don't need to. Simply pass your object array to the method, modify and it will reflect from the called place. There is no pass by value in java. There's no pass by reference in Java.

inventory.filter(fruit => fruit.quantity === 5).map(fruit => ({ name: fruit.name, type: fruit.type }));

map creates a new array using the values you give it, but doesn't change the original, filter creates an array using only the values the function returned a truthy value for.

Array, Arrays are list-like objects whose prototype has methods to perform traversal and mutation operations. in the array, JavaScript arrays are not guaranteed to be dense; this The array's object properties and list of array elements are separate​, and the Using an invalid index number returns undefined . 7.5 Returning Array from Methods. A reference to an array can be returned from a method, look at the following program : /** * This program demonstrates how a reference to an * array can be returned from a method.

You can remove the type property by destructuring:

const inventory = [
    {name: 'apples', quantity: 2, type: 'a'},
    {name: 'bananas', quantity: 0, type: 'a'},
    {name: 'cherries', quantity: 5, type: 'a'},
    {name: 'mangos', quantity: 5, type: 'a'}
];

const res = inventory.map(({type: x, ...rest}) => rest);

console.log(res);

Data Structures: Objects and Arrays :: Eloquent JavaScript, Almost all JavaScript values have properties. The exceptions Both value.x and value[x] access a property on value —but not necessarily the same property. This example demonstrates two methods you can use to manipulate arrays: You give it an object, and it returns an array of strings—the object's property names. A method can return a reference to an array. The return type of a method must be declared as an array of the correct data type.

Try using lodash

const inventory = [
    {name: 'apples', quantity: 2, type: 'a'},
    {name: 'bananas', quantity: 0, type: 'a'},
    {name: 'cherries', quantity: 5, type: 'a'}
    {name: 'mangos', quantity: 5, type: 'a'}
];

const result = ._map( inventory, (item)=> { 
    return {
             name: item.name, 
             quantity: item.quantity}
} );

Useful Javascript Array and Object Methods, With all these array and object methods you'll find you never have to reach for The returned value can be of any type (i.e. object, array, string, integer). do things likes flattening an array of arrays, grouping objects by a property, and It should be noted that spreading objects does not do nested copying. Allows for objects to be combined together. This method is not really needed because you can use the object spread syntax instead. Like the object spread operator, Object.assign() does not do deep cloning. Lodash is your best friend when it comes to deep cloning objects. Example. Combine two objects into one.

Advanced Javascript: Objects, Arrays, and Array-Like objects, Javascript objects and arrays are both incredibly useful. They're Setting a string parameter adds to the underlying object arr.length; // returns 2, not 3. The length property is only modified when you add an item to the array, not the Array.​prototype :This gives us access to all the methods properties that each array inherits. Object Definitions Object Properties Object Methods method also joins all array method does not change the existing arrays. It always returns a new array.

JavaScript Arrays, And what if you had not 3 cars, but 300? The typeof operator in JavaScript returns "object" for arrays. The real strength of JavaScript arrays are the built-in array properties and methods: Tutorials, references, and examples are constantly reviewed to avoid errors, but we cannot warrant full correctness of all content. You don't need to return anything. The way Java handles arrays, when you use the method it changes the contents of the original array. Thus, you can just print it as is.

jQuery.each(), Arrays and array-like objects with a length property (such as a function's arguments The $.each() function is not the same as $(selector).each(), which is used to iterate, The method returns its first argument, the object that was iterated. If the only argument passed to the Array constructor is an integer between 0 and 2 32 -1 (inclusive), this returns a new JavaScript array with its length property set to that number ( Note: this implies an array of arrayLength empty slots, not slots with actual undefined values). If the argument is any other number,

Comments
  • If you want a new object with fewer properties, then return a new object. Seems like you first want to .filter() with the given predicate before mapping the new objects though.
  • FYI, your line inventory.map( fruit => fruit.quantity === 5 ); will return an array of true/false values. Not sure if that's what you're after there.
  • map(({ quantity, ...rest }) => rest)
  • @CrazyTrain rest is already an object, no need to create an object from an object.
  • @Li357: Ah yeah, you're right. For some reason I thought it returned a temporary collection like .entries() returns.
  • Why lodash's map instead of the method by standard?