Javascript Reference Object Property By Variable
These named values are usually referred to as properties of the object. Let b a.
A property has a key also known as name or identifier before the colon and a value to the right of it.
Javascript reference object property by variable. In the code snippet below the variable magneto is a compound value Array object thus it is assigned in variable function argument x with assign-by-reference. Lets see how each syntax to access the properties work. Copy the reference alert a b.
Person x The expression must evaluate to a property name. The second one has the name age and the value 30. Const property object.
A variable myName is created and is given the value of an object which has a property called firstName. FirstName has the value of Carlos. A JavaScript object is just a collection of named values.
Therefore if youve an objects property name stored in a JavaScript variable you can get its value using the square bracket notation as shown. But we can also access the value using a variable key. Javascript Object Oriented Programming Front End Technology.
We know that an object value can be accessed by using a Dot notation or Bracket notation. Var obj property_1. Objects are copied by reference instead of by value.
True both variables reference the same object alert a b. Lets look over them in a nutshell. The syntax for accessing the property of an object is.
Where the dot notation is easier to read and write the square bracket notation offers much more flexibility since the value between the brackets can be any variable or expression. Var refCopy reference. Let a.
Where obj is the name of the new object each property_ i is an identifier either a name a number or a string literal and each value_ i is an expression whose value is assigned to the property_ i. The code above looks like this in memory. In Pass by Reference Function is called by directly passing the referenceaddress of the variable as the argument.
The resulting user object can be imagined as a cabinet with two signed files labeled name and age. When a function is called the arguments to the call are held in the array-like variable arguments. ObjectName property person age or.
ObjectName expression x age. True And here two independent objects are not equal even though they look alike both are empty. Var reference 1.
What is really happening can be described as follows. The static keyword defines a static method for a classStatic methods arent called on instances of the class. Changing the argument inside the function affect the variable passed from outside.
Here the output is the same for the variables containing objects. That happens because when dealing with objects the operator works by reference. There are two ways to access or get the value of a property from an object the dot notation like objfoo and the square bracket notation like obj foo.
Instead theyre called on the class itself. When a reference type value an object is copied to another variable using the address of that value is whats actually copied over as if it were a primitive. How to create an object property from a variable value in JavaScript.
If you remember from the JavaScript arrays chapter an array is a collection of values where each value has an index a numeric key that starts from zero and increments by one for each value. Square brackets property access. The first property has the name name and the value John.
Creates a new object with the specified prototype object and properties. In the user object there are two properties. You can access the properties of an object in JavaScript in 3 ways.
These are often utility functions such as functions to create or clone objects.
