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Introduction to JavaScript

Properties

When you introduce a new piece of data into a JavaScript program, the browser saves it as an instance of the data type. An instance is an individual case (or object) of a data type.

JavaScript will save a new piece of data, like 'Hello', as a string instance in the computer's memory. Another example, the number 40.7, is stored as an instance of the number data type.

An instance, like the string 'Hello', has additional information attached to it.

For example, every string instance has a property called length that stores the number of characters in it. You can retrieve property information by appending the string with a period and the property name:

console.log('Hello'.length);

In the example above, the value saved to the length property is retrieved from the string, 'Hello'. The program prints 5 to the console, because Hello has five characters in it.

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