parseInt vs Unary Plus: Which Should You Use to Convert Strings to Numbers?

parseInt vs Unary Plus: When to Use Which?

Introduction:
When converting strings to numbers in JavaScript, developers often debate between using parseInt or the unary plus ( ) operator. This article aims to clarify their differences and guide you in choosing the appropriate approach.

Core Differences:

• Return Types:

  • parseInt: Returns a whole number.
  • Unary plus: Returns a number, which may be an integer or floating-point.

• Coercion Rules:

  • parseInt: Tries to coerce the string to a base-10 integer.
  • Unary plus: Simply evaluates the string as a number expression.

Performance:

Performance tests indicate that the unary plus operator is generally faster than parseInt, particularly in recent Chrome versions.

When to Use parseInt:

Use parseInt when you specifically need a whole number and want to handle non-numeric characters gracefully:

When to Use Unary Plus:

Prefer the unary plus operator when you need either an integer or a floating-point number:

Caveats:

• Leading Whitespace: parseInt ignores leading whitespace, while the unary plus operator does not.
• Base Specifier: parseInt accepts a second argument to specify the numeric base (e.g., 10, 16). The unary plus operator does not.
• NaN Return: Both parseInt and the unary plus operator return NaN for non-numeric strings.

Double Tilde Operator (~~):

The double tilde operator (~~) is similar to parseInt, as it attempts to convert a string to a whole number. However, it differs in the following ways:

• Always rounds towards zero.
• Does not handle non-numeric characters gracefully.
• Is less precise than parseInt.

Conclusion:

Use parseInt when you need a whole number with controlled coercion, and use the unary plus operator when you don't require special handling or performance is critical. Choose the double tilde operator sparingly, considering its limitations.

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