How to push an object in an Array

const animals = ['pigs', 'goats', 'sheep'];

animals.push({animal: 'cows'});

console.log(animals); // ["pigs", "goats", "sheep", { animal: "cows" }]

Use the Array.prototype.push method to append values to the end of an array:

Copy// initialize array
var arr = [
  "Hi",
  "Hello",
  "Bonjour"
];

// append new value to the array
arr.push("Hola");

console.log(arr);

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You can use the push() function to append more than one value to an array in a single call:

Copy// initialize array
var arr = ["Hi", "Hello", "Bonjour", "Hola"];

// append multiple values to the array
arr.push("Salut", "Hey");

// display all values
for (var i = 0; i < arr.length; i++) {
  console.log(arr[i]);
}

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Note that the push() method returns the updated length of the array.

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Update

If you want to add the items of one array to another array, you can use firstArray.concat(secondArray):

Copyvar arr = [
  "apple",
  "banana",
  "cherry"
];

// Do not forget to assign the result as, unlike push, concat does not change the existing array
arr = arr.concat([
  "dragonfruit",
  "elderberry",
  "fig"
]);

console.log(arr);

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Update

Just an addition to this answer if you want to prepend any value to the start of an array (i.e. first index) then you can use Array.prototype.unshift for this purpose.

Copyvar arr = [1, 2, 3];
arr.unshift(0);
console.log(arr);

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It also supports appending multiple values at once just like push.

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Update

Another way with ES6 syntax is to return a new array with the spread syntax. This leaves the original array unchanged, but returns a new array with new items appended or prepended, compliant with the spirit of functional programming.

Copyconst arr1 = [
  "Hi",
  "Hello",
  "Bonjour",
];
const arr2 = [
  "Ciao",
  "Hej",
  "Merhaba",
];

const newArr1 = [
  ...arr1,
  "Salut",
];
const newArr2 = [
  "Salut",
  ...arr2,
];
const newArr3 = [
  ...arr1,
  ...arr2,
];

console.log(newArr1, newArr2, newArr3);

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Use the concat function, like so:

var arrayA = [1, 2];
var arrayB = [3, 4];
var newArray = arrayA.concat(arrayB);

The value of newArray will be [1, 2, 3, 4] (arrayA and arrayB remain unchanged; concat creates and returns a new array for the result).

Objects behave a bit differently from most other datatypes in JavaScript. When you assign an object to a variable or add it to an array or anything like that. JavaScript does not make a copy of the object, it makes the new variable (or array item) contain the exact same object you assigned. To illustrate this take a look at this code: ```JavaScript var example = { message: "Hello" }; var example2 = example; example.message = "world"; console.log(example2); ``` We create an object example then we create a new variable example2 and assign example to it. Then we change the message property of example and then we print out example2. Now what do you think will be printed out? If Objects worked like Strings and Numbers then you would expect { message: 'Hello' } to be printed out. Since that is what example contained when it was assigned to example2. But in reality the above code prints out { message: 'world' }. This is because these two variables don't hold independent copies of the object, they hold the exact same object. Which means that even though there are two variables at play there is actually only one object created in the above code. You just have two variables pointing at it. With that knowledge if you take a look at your code the behavior you experience should make a bit more sense. You create one object at the start of your code, then you assign it the details of one student. Then you add a pointer to that object to the array. Then you change that same object with details of a new student. Since you in reality only have one object you end up changing the values of that one object each time the loop runs. And adding that object to the array multiple times just creates multiple pointers to it. The solution to this issue is quite simple. Just create the object within the loop. Like this: ```JavaScript alert ("Hello"); var students = []; var tempNewStudentStorage; var finished; var questions = [ "What is the student's name?", "What Track(s) are they on?", "What achivement(s) have they gotten?", "What are their points?", ]; while (true) { var newStudent = { Name: "x", Track: "y", Achivement: 0, Points: 0, }; for (var i = 0; i < 4; i +=1) { tempNewStudentStorage = prompt(questions[i]); if (i === 0){ newStudent.Name = tempNewStudentStorage; } else if (i === 1){ newStudent.Track = tempNewStudentStorage; } else if (i === 2){ newStudent.Achievemnt = tempNewStudentStorage; } else if (i === 3){ newStudent.Points = tempNewStudentStorage; }; }; students.push(newStudent); finished = prompt("Are you done adding students? Y/N").toLowerCase(); while (finished.length > 1) { finished = prompt("Are you done adding students? Y/N").toLowerCase() }; if (finished === "y") { alert("Thank you for adding a new student!") break } else if (finished !== "y"){ continue; }; }; console.log(students); ``` That way you actually create a new object each time the loop runs, instead of reusing the object created at the start of the script. It's worth noting that Arrays and Functions also behave in the same way as I described above.

Arrays in javascript are not the same as an array in C. In C you'll allocate a new array with type and a fixed size and if you want to alter the size you'll have to create a new one. For javascript arrays on the other hand if you have a look at the description of arrays over at MDN you'll see this line.

Arrays are list-like objects whose prototype has methods to perform traversal and mutation operations. Neither the length of a JavaScript array nor the types of its elements are fixed. Since an array's length can change at any time, and data can be stored at non-contiguous locations in the array

So while it is called "array" it is more like a list which lets you resize it freely (and also store anything, because javascript).

There is also another question about the semantics of the push/pop methods here on SO that can shine some more light on those: How does the Javascript Array Push code work internally