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JavaScript Type coercion and conversion

Type coercion and type conversion in JavaScript are ways to change a value from one data type to another. Type coercion is the automatic conversion of a value from one data type to another, while type conversion is an explicit way of converting values between different data types.

  1. Type coercion:

Type coercion happens implicitly when JavaScript tries to operate on values of different data types, or when it evaluates expressions in a specific context that requires a particular data type. JavaScript will automatically convert values to the expected data type to perform the operation or evaluation. There are three main types of type coercion in JavaScript: string coercion, numeric coercion, and boolean coercion.

  • String coercion: Occurs when a value is expected to be a string. For example, when using the `+` operator with a string and a non-string value, JavaScript will coerce the non-string value to a string.
var number = 42;
var string = "The answer is: ";
console.log(string + number); // "The answer is: 42"
  • Numeric coercion: Occurs when a value is expected to be a number. For example, when using arithmetic operators with non-numeric values, JavaScript will coerce the values to numbers.
var stringNumber = "42";
console.log(10 + +stringNumber); // 52
  • Boolean coercion: Occurs when a value is expected to be a boolean. For example, when using a value in a conditional expression, JavaScript will coerce the value to a boolean.
var string = "Hello, World!";
if (string) { // The string is coerced to a boolean
  console.log("The string is truthy");
}
  1. Type conversion:

Type conversion, also known as type casting, is the explicit conversion of a value from one data type to another. There are several built-in methods and constructors in JavaScript that can be used for type conversion:

  • `String()`: Converts a value to a string.
var number = 42;
var stringNumber = String(number);
console.log(typeof stringNumber); // "string"
  • `Number()`: Converts a value to a number.
var stringNumber = "42";
var number = Number(stringNumber);
console.log(typeof number); // "number"
  • `parseInt()` and `parseFloat()`: Parse a string and return an integer or a floating-point number, respectively.
var stringInt = "42";
var stringFloat = "3.14";
var intNumber = parseInt(stringInt);
var floatNumber = parseFloat(stringFloat);
console.log(intNumber, floatNumber); // 42 3.14

  • `Boolean()`: Converts a value to a boolean.
var string = "Hello, World!";
var boolValue = Boolean(string);
console.log(boolValue); // true

Understanding the difference between type coercion and type conversion is crucial when working with JavaScript, as it can lead to unexpected behavior if not handled correctly. Type coercion is the automatic conversion of values between data types, while type conversion is the explicit conversion of values. Being aware of these concepts will help you write more predictable and reliable JavaScript code.

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