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What will happen when [50,100] is converted to Number in JavaScript?

HTML Javascript Programming Scripts

Use the Number() method in JavaScript to convert to Number. When an array like [50, 100] is converted to Number in JavaScript, the result might be surprising.

What Happens with Array to Number Conversion?

When Number() is called on an array, JavaScript first converts the array to a string, then attempts to convert that string to a number. For arrays with multiple elements, this results in NaN (Not a Number).

Example

<!DOCTYPE html>
<html>
   <body>
      <p>Convert [50,100] to Number</p>
      
      <script>
         var myVal = [50,100];
         document.write("Number: " + Number(myVal));
      </script>
      
   </body>
</html>

Number: NaN

Why Does This Happen?

The conversion process follows these steps:

let arr = [50, 100];

// Step 1: Array converts to string
console.log("Array to string:", String(arr));  // "50,100"

// Step 2: String converts to number
console.log("String to number:", Number("50,100"));  // NaN

// Final result
console.log("Final result:", Number(arr));  // NaN

Array to string: 50,100
String to number: NaN
Final result: NaN

Different Array Cases

console.log("Empty array:", Number([]));           // 0
console.log("Single element:", Number([50]));      // 50
console.log("Multiple elements:", Number([50,100])); // NaN
console.log("String element:", Number(["hello"])); // NaN

Empty array: 0
Single element: 50
Multiple elements: NaN
String element: NaN

Comparison Table

Array	String Representation	Number() Result
`[]`	`""`	`0`
`[50]`	`"50"`	`50`
`[50, 100]`	`"50,100"`	`NaN`

Conclusion

Converting [50, 100] to Number results in NaN because the array becomes the string "50,100", which cannot be parsed as a valid number. Only single-element numeric arrays convert successfully to numbers.

Sai Subramanyam

Updated on: 2026-03-15T23:18:59+05:30

165 Views

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