JavaScript Type Conversion

JavaScript provides ways to convert data from one type to another, which is known as type conversion. There are two main types of type conversion: implicit (type coercion) and explicit (type casting).

1. Implicit Conversion (Type Coercion)

JavaScript automatically converts types when it expects a certain type in an operation.

Examples:

• String Concatenation:

  let result = "5" + 2;  // "52" (Number 2 is converted to a String)
  

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• Numeric Operations:

  let result = "5" - 2;  // 3 (String "5" is converted to a Number)
  

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• Boolean Contexts:

  if ("") {
    console.log("This won't log"); // Empty string is coerced to false
  }
  

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2. Explicit Conversion (Type Casting)

You can explicitly convert types using various methods.

2.1 Converting to String

• Using String():

  let num = 123;
  let str = String(num); // "123"
  

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• Using .toString():

  let bool = true;
  let str = bool.toString(); // "true"
  

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2.2 Converting to Number

• Using Number():

  let str = "123";
  let num = Number(str); // 123
  

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• Using parseInt() and parseFloat():

  let strInt = "123";
  let strFloat = "123.45";
  let intNum = parseInt(strInt);    // 123
  let floatNum = parseFloat(strFloat); // 123.45
  

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2.3 Converting to Boolean

• Using Boolean():

  let val = 0;
  let bool = Boolean(val); // false
  

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3. Common Conversion Scenarios

3.1 String to Number:

let str = "456";
let num = +str;  // 456 (Unary plus converts string to number)

3.2 Number to String:

let num = 789;
let str = num + ""; // "789" (Concatenation converts number to string)

3.3 Boolean to Number:

let bool = true;
let num = +bool; // 1 (true is converted to 1)

3.4 Falsy to Boolean:

Values like 0, "", null, undefined, NaN, and false are converted to false.

console.log(Boolean(""));    // false
console.log(Boolean(0));     // false
console.log(Boolean(null));  // false