JavaScript Type Conversion

In JavaScript, values can be converted from one data type to another either automatically (type coercion) or manually (type casting). This process is known as type conversion.

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Implicit Type Conversion (Type Coercion)

JavaScript automatically converts data types when needed. This is known as type coercion.

let result = "5" + 2;
console.log(result);  // "52" (number 2 is converted to a string)

Here, JavaScript converts the number 2 to a string and performs string concatenation.

let result = "5" - 2;
console.log(result);  // 3 (string "5" is converted to number)

In above case, the – operator forces both operands to be treated as numbers.

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Explicit Type Conversion (Type Casting)

You can manually convert values using built-in functions.

Convert to String

String(123);            // "123"
(123).toString();       // "123"

Convert to Number

Number("123");          // 123
parseInt("123.45");     // 123
parseFloat("123.45");   // 123.45

You can also use parseInt() or parseFloat():

let price = "99.50";
console.log(parseInt(price));   // 99
console.log(parseFloat(price)); // 99.5

Convert to Boolean

Boolean(1);             // true
Boolean(0);             // false
Boolean("");            // false
Boolean("hello");       // true

Values like false, 0, “”, null, undefined, and NaN are considered falsy. All others are truthy.

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Summary

Operation	Result	Explanation
“5” + 2	“52”	Number converted to string
“5” – 2	3	String converted to number
true + 1	2	true becomes 1
Number(“123.45”)	123.45	String to number
Boolean(“”)	false	Empty string is falsy
Boolean(“hello”)	true	Non-empty string is truthy

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Why Type Conversion Matters

• It prevents unexpected behavior in your code
• It helps in handling form inputs (which are strings)
• It’s essential for proper comparisons and calculations

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Best Practices

• Avoid relying on implicit conversion in important logic.
• Prefer explicit conversion to make code clear and bug-free.
• Use === instead of == to avoid unintended type coercion.

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