To declare an array in JavaScript, you can use the square brackets notation. Here's an example:

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let colors = ["red", "blue", "green"];

In this example, the variable colors is declared as an array with three elements: "red", "blue", and "green". You can access and modify individual elements of the array using their index. For example, colors[0] refers to the first element of the array, which is "red".

To create an array with objects inside, you can use curly braces {} to define each object and square brackets [] to wrap the array. Here's an example in JavaScript:

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// Creating an array with objects inside
let myArray = [
  { name: 'John', age: 25 },
  { name: 'Jane', age: 30 },
  { name: 'Bob', age: 35 }
];

console.log(myArray);

Output:

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[
  { name: 'John', age: 25 },
  { name: 'Jane', age: 30 },
  { name: 'Bob', age: 35 }
]

In this example, we created an array called myArray that contains three objects. Each object has properties such as name and age.

To console log properties in an object using square brackets, you can follow these steps:

1. Create or access an object with properties.
2. Use square brackets and the property name inside to access the value of that property.
3. Pass the object with the square brackets notation to console.log() to print the value of the property to the console.

Here is an example in JavaScript:

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const myObject = {
  name: 'John',
  age: 25,
  city: 'New York'
};

console.log(myObject['name']); // Output: John
console.log(myObject['age']); // Output: 25
console.log(myObject['city']); // Output: New York

Note that you can also use dot notation (myObject.name, myObject.age, myObject.city) to access the properties of an object. Square brackets are useful in situations where the property name is stored in a variable or when the property name contains special characters or spaces.

You can target an object key in an alert box by using the object name followed by the key name in square brackets. Here's an example:

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let person = {
  name: 'John',
  age: 30
};

// Targeting object key in alert box
alert(person['name']); // will display 'John'

You can also use dot notation to access the object key instead of square bracket notation:

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let person = {
  name: 'John',
  age: 30
};

// Targeting object key in alert box using dot notation
alert(person.age); // will display 30

Square brackets are used in programming languages like JavaScript to access or specify the index of an item stored in an array or an object. For example, in JavaScript, you can access the first element of an array named myArray using myArray[0]. Here [0] is the square bracket syntax used to access the element at index 0 of the array. Here's an example:

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const myArray = [1, 2, 3, 4, 5];
console.log(myArray[0]); // outputs 1

To make a 2D array an argument of a function in C++, you can declare the function with the array parameter using square brackets for both dimensions.

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void myFunction(int myArray[][3]) {
  // function body here
}

In this example, myFunction() takes a 2D integer array as an argument. The size of the second dimension must be specified, while the size of the first dimension can be left empty or specified. In this case, the second dimension has a size of 3.

Here's an example of calling this function with a 2D array argument:

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int main() {
  int array2D[2][3] = {{1,2,3}, {4,5,6}};
  myFunction(array2D);
  return 0;
}

In this example, main() declares a 2D integer array called array2D, which is then passed as an argument to myFunction(). The function can then access or modify the elements of the array as needed.